Don't go replacing your battery expecting to fix a cooling fan issue and here is why. By the way, epic fail by MB to have the cooling fan kick on when the ECU sees a low voltage situation. I just replaced the battery in my C280 because someone put the wrong size battery in it. I opted for the factory replacement since no one around here had the correct size, physical size , none were long enough to use the battery hold down clamp on the end. You never want a battery sliding around under the hood , ever. Anyways $180 at the dealer for the battery , installed it my self. Right after I installed the new battery I realized the fan was kicking on when the car would sit for a while, then in would cycle on and off , then it would randomly just stay on full high speed all of which happened with engine off and key out of ignition , like it has a mind of its own. At the time I thought it had something to do with the key fob issues I was having so I just disconnected the battery , then had to have car towed to dealer for the key fob issue which is another long post all together, lol. Anyways I have my key fob issue squared away , I have a new battery from the dealer in the car AND the cooling fan is still kicking on at random times. Sometimes it will stay on , sometimes it will pulse real fast on and off , sometimes it will stay off. From all the reading I have done so far there is a 90% chance its the ECU . I like this C280 but MB just over engineered the crap out of the electronics making it difficult even for the most experienced do it yourselfers to diagnose and repair so you have to go back to the dealer and spend big bucks to have it repaired.
Thanks for this! Had the exact same problem. Got to my car after work, battery completely dead. Very strange, as I had recharged it, just as a precaution, a few days ago, as some little electrical niggles had started. Thankfully the lady who had parked in front of me got to her car at the same time and let me know the fan had been running on high when she got there. Obviously what had drained the battery... I tried jump-starting the car and as soon as it had enough charge, the fan came on again and drained all the charge - so much so that I couldn't jump start it. Disconnected the fan, jump started the car and reconnected the fan so I could drive home. Have now disconnected the battery and put it on a recond-charge. Been 12 hours, still not fully charged - think it's time for a new one! Thanks for saving me a lot of head-scratching!!
Hey guys. In my case the block heater caused the problem. I live in Canada and I have to plug it to keep it warm when the temperature is too cold. I put a trikle charger (Noco Genius 2G) that means the battery is always on the right voltage. I conected together under the hood with the block heater. But.... I forgot to put a timer to turn them on and off every 15 or 30 minutes. My block heater was working and overheated my coolant for 5 days nonstop. The sensor was detecting 100 degrees for that time. I solved uplugging it for 2 or 3 days and letting the temperature dropps to cero degrees. I started it again with the coolant cold and the problem was solved. Sometimes you fix the issue not because you are replacing the battery... You are fixing the problem cause you are reseting the computer unplugging the battery for at least one minute. It was my experience.
Just wanted to say thank you. This exact thing happened to my daughters C300 yesterday. I got a new AGM battery today and the fan stopped running when shutoff.
I had EXACTLY the same problem with my ML430. It's one of those strange things. It makes absolutely no sense. The battery that I take out of the ML gets put into one of the other cars and gives a few more years of service (This has happened more than once). Once the ML has a new battery the fan works and powers down and a few more gremlins stop acting up (at night the radio backlight doesn't switch on sometimes). I even tried to put a new battery from one of the other cars that is underspecked and it also gave me the glitches. I tried with a 8A charger connected and the battery fully charged and it still glitched. The only solution even though it makes ABSOLUTELY NO SENSE is to replace the battery with a good quality NEW battery. The battery drain issues also stop with the new battery. I have also noticed that it happens after the battery has been discharged once in its life where it has insufficient power to start the engine just once. After recharging it appears to be okay but it isn't.
My Vito115 does the same thing. Once the battery reaches a certain age the van drains the battery (via the computer fam) until a new one is installed. My SL320 has a marvelous feature. when the battery goes low it disconnects thereby preventing battery damage. Just a few minutes of charging and the car is good to go. My 280SL is still the most reliable car ever nearly no electronics.
Sounds exactly right. Thanks for the overview. Most people don't realize there are more parameters to battery than just storing 12V. The sense circuit is just a little too sensitive. I get the logic behind the car killing the battery so you'll replace it but, in practice, it could leave you stuck. Because even my little booster pack I keep in the trunk would just cause the fan to come on full blast, you'd have to unplug the fan header, start the car then plug it back in with the car running. Not a great situation.
thus is NOT a feature, it is a bug of the battery Management. Fear not the newer Benz still retain this battery drain. Tons of heavy duty 1st tier AGM batteries get discarded for no good reason. The issue is tied with the reading of battery sensor over the CAN-BUS or lack of communication with it through "gateway module".... Use "worskop menu" to display batt. voltage on the dashboard while driving... witness what is happening !!
I have a similar issue on 2009 ML320. It's a grounding problem with the blower motor, which is costly to replace. Under the glove compartment take down the panel and you will see a connector to the blower motor. I just wired it directly to manually turn on/off through a switch. Copied from another thread
You had an internal crack or break at the post, on your battery.. unique issue. Thats caused by hitting the post with excessive impact or overtightening the battery clamps, causing the battery post to flex and resulting damage.
I'm having a similar problem right now.(2011 c300) I left my lights on and the battery was dead in the morning, now once I charge it, it works but then the fan continues to run, which I think is draining it, so then it dies again. Took it to where I bought it, they think its a module or a sensor, nobody seems to want to listen to my suggestion about the fan running because of the bad battery. They have me bringing to their Mercedes specialist for a second opinion. I called the dealer they want $165 and hour just to diagnose.
Hi Melissa, sorry to hear you're having problems. Let's see if we can narrow it down. Do you know how old the battery is? And did you measure the voltage in the morning when you realized it was dead? From what you've said so far, it's possible to ruin battery by discharging it down to a really low level. Which leaving your lights on could do. Especially if the battery is a little older. It reduces it's capacity to hold charge and the computer on these cars is very sensitive to a battery not being in spec. I'd start by load testing the battery, looking at the voltage before and after a charge cycle as well. Even if it tests ok, I'd see if I could get another battery to even hook up temporarily and see what it does. If the battery is anywhere near 5 years old, I'd just replace it. If a scan has already been done with a Mercedes specific scan tool, it's unlikely the star diagnostics would be able to tell you anything more. It is possible for a fan module or ecu, or engine temp sensor to go bad but there would more than likely be an error code.
The battery is actually only 11 months old, which is why I thought one night with the lights on wouldn't be that big a deal. Unfortunately I don't have a voltage checker (that may be little out of my skill set) luckily they are sending it to their Mercedes mechanic for me who isn't going to charge to diagnose. I just like to be as educated as possible. It's weird because even though the lights were turned on (not auto) they were not actually on (like shining light) My car does this strange thing when it rains, where the "Auto Light Inoperative" warning comes on and the wipers don't work, this was happening the other day, which was why I turned the switch to on. This is also something no one has been able to figure out. Have you heard or had that issue?
Oh ok, it could still be a bad battery but with that information it sounds like the issue is elsewhere. If you're not comfortable with a multimeter or load tester, best leave it to a mechanic you trust. I haven't heard of that issue specifically. When it comes to diagnostics, multiple things happening at once are rarely a coincidence. I could guess at what the issue is all night but what you need are some initial measurements so you can break the problem down to smaller levels until you isolate it. With any problem, there can be many things that would cause it. I hope you can get it figured out and report back. I'd love to hear what you or your mechanic find.
So I just heard back from the mechanic (literally had the car this whole time) and they said that the satellite radio, which I don't use or even knew I had, was continually running and that was what was draining the battery and causing the fan to run. So since I don't use it the fix is going to be to just disconnect it. They are charging me $390 for the diagnostic and fix, which I guess is better than the dealer would have. But still a little frustrating. Not sure what I think at this point, any thoughts?!?
My car (2008 c300) just did the exact same thing tonight. I noticed it turned on without the key anywhere near the car. when i unlocked / locked the car, the fan would shut off for a minute; then turn right back on. Did this several times before I disconnected the battery. Ill have to deal with it tomorrow night when the stores are open. I noticed its the original battery as well. Hoping thats my issue. On a side note, I will have a video posted tomorrow of s funky thing my nav screen is doing. If you wouldn't mind taking a look and seeing what you think, that would be great! it has a mind of its own, that's for sure!
I can't guarantee it but, it could likely be a bad battery. The computer is always monitoring it and if it falls out of spec it will start killing it by running the fan so you'll replace it. And it's not unlikely that a bad battery wouldn't cause other issues. The other thing to check, with the car on, does the temperature gauge respond normally? (show cold when first starting in the morning then gradually come to operating temp and stay above 80) If not, it could be a temperature sensor. It's also possible that the fan control module is bad. Given what you've told me, these are less likely. If it's the original battery, change it, it's old enough you'll start having problems anyway. And I will take a look at your video for sure. Good luck!
I have the exact same issue for 2 nights in a row. The car is currently in a service, and i've told the guys not to replace the battery in order not to kill a brand new battery, but to try to find the problem, and couple of days after they're still unable to find where the problem might be. I'm a bit concerned about the ECU as it is the most expensive opiton in that case, but still, I might ask them to try with a brand new, quality battery. Almost forgot to mention, they tried with brand new fan kit (including the fan module and everyting) but the car have had the same issues. I've also having the fan on full speed even when the car is on, and once I turn the ignition off, and wait for a couple of hours, the fan ramps up and kills the battery. My current battery is about 4y old, could you please share any thoughts on this, and whether you managed to fix the problem by replacing the either battery or ECU?
hey man im having the same problem. Sometimes the fan would turn on after shutting the car off, but it would only come on for a quick few secs, than shut off. Than sometimes my fan would work during idling and than it wouldnt work and would overheat my car... Than it would fully work with ac and heat on. I just changed the battery and it still the same and i changed the coolant thermosttat and still the same.
I have a 2002 E320 that has a similar problem. I’m thinking because I have a significant battery drain problem, I’m sure it’s the radio that’s causing the drain. I jump started the car wash he other day and the blower fan came on without being turned on . I switched the car off and it continued to run full blast! Could this be from jump starting car and the computer going haywire?
I have a same issue with my fan Some days after turn off engine fan will go fast and stop suddenly, after 20 to 30 min unlock my car it will start again in full speed and off, when car is running temp wil go to 100 c suddenly drop of to 80 c and sign of tempture will turn on and off, after turn off the car for 10 min every thing will run normal again in some days in traffic temp raise near over heating in 120 c i checked fan not working
Maybe you can help me, I know what caused my problem. I had been looking at my fuses to try to disable the car alarm that kept going off randomly. I did not even touch the fuses as I figured I would later that day and my big mistake was leaving the fuse cover off since I knew I would be back later on. The problem is I went for gas and figured why not get a car wash. I did and as I came out of the wash I heard the radiator fan louder than usual. I pulled off to the side of the car wash and turned off the engine and then the fan came back on .... I pulled out the key and it still stayed on. Then I opened the hood and I saw that I had left the fuse box cover off and looked closer and I saw some small drops of water on the fuses. Murphy's Law. I left the cover off and then got a car wash and water had somehow sprayed under the bonnet. A bad coincidence. I dried it off as best I could. The fan stayed on. I drove it home and it stayed on even without the key. Right now I have the negative terminal off the battery to stop the fan. I will readdress the problem in the daylight tomorrow. Any thoughts ?
If you're convinced the problem is in the fuse box, it will likely be fixed once the excess water dries up. A couple drops of water in the fuse box shouldn't be a big deal but if you're not sure how much got in, it needs to be flushed from around any contacts to prevent corrosion. You may need to pull some or all the fuses and relays. Either way, isopropyl alcohol (over 90% if you can get it) and slowly pour it over the whole area of contacts, there should be a drain in the box and this will dilute and flush most of the water. You don't have to use the whole bottle. Next step is to get a hair dryer on a lightly warm setting and heat the whole interior of the fuse box so any other moisture and alcohol will evaporate off. Be careful! Was the engine temperature gauge in the normal range? You could have a bad thermostat. It is also possible for the fan control module to go bad. Also check your battery is good and the cables are securely fastened and no excessive corrosion on the terminals or cables. Coincidences do happen sometimes so don't assume anything. Good luck!
@@merczero1184 The temperature was not abnormal ... night time .... cool weather. I am convinced it is because I left the cover off before I did the car wash ... it all occurred right after the car wash and it was zero problem before. I sure hope that I did not cause a short. Thanks ... will do all that you advise !
@@nimeshobha I wrote you a long detailed answer and before I sent it my cell died and the response vaporized. So here goes once again. I felt the problem was caused by the water getting into my fusebox, so in the morning I reconnected the battery, and I sprayed the open fuse box with WD-40 and I left the cover off and drove for around ten minutes thinking the hot air blowing around would dry out the fuse area. It did. the problem cured itself. As for the pulling the fuse that competes the circuit for the alarm ..... I have yet to do that. It seems to be one of two 7.5 amp brown fuse in the engine fuse box. The alarm going off .... which was the root of my problem ... has only happened a few times since. I do not set the alarm by locking the car and thereby it does not go off. If I do set the alarm and IF it does go off on it's own .... I go out to the car and put the key in and it goes off. Obviously it is not safe to leave the key in so I put my other car behind the Merc to block the driveway ....... I know that once I have the time I can test pull the brown fuses and determine which one kills the alarm horn.
@@funguy4utube Dude this is 100% exact same issue that happened to me with my 2005 CLK-320. First my alarm messed up, pulled 7.5amp brown fuse in rear SAM. Then i was messing with front cover, left it off drove to work and it rained. Needed a jumpstart to get home, and suspected that was the issue ! This is crazy hahaha.
use the "secret workshop menu" to display batt voltage on the dashboarf while driving - You'll see how the computer wants to charge your battery ! Max 14.9v into AGM while cold Above 12.6v it is charging ok Below 12.4v it's draining power Below 11.9v dont drive too far! "Whorkshop menu" is invoked prior to engine start sequence 👍🏻
I’m having a similar issue but my car battery got changed and now it still says transmission not in park risk of rolling away and anti theft enabled and vehicular is immobile
Sounds like you need to do some diagnostics. If all those problems happened at or around the same time, assume they are all from the same source until proven otherwise. If you're not up to the task of hunting down electrical problems, bad sensors, switches, connectors, wiring etc. just save yourself the frustration and take it to a garage.
Guys my problem is little diff, w204, c200 (petrol) 2009, today i had a engine heat signal so i quickly changed coolent (it was low), within few seconds after the warning sign i stopped and put coolent. Now my fan keeps on running, even after switching my engine off. I waited for 20 minutes still it was running. Finally disconnected the battery. Hope changing battery will help.
MercZero11 hey, once the temperature indicators came I immediately stopped my car, may be 5 meters or 10, coz i just went to get some drinks near my house. (Maximum 1.5 miles the car has run post which i saw the indicator ) the car is hardly used. Now once i stopped at put water first the temps gauge never went up neither i saw any warning. Now i just asked the battery company to take a dif battery and check but same issue. My battery volt 12.25 new battery volt 12.55. What to do :(
@@james2k00 Unless the battery was drained to a really low voltage and/or sat for a long time , I'd try charging it first. Possibly even cycling it to full charge then discharge a few times. As I say in the video, normal battery voltage reading during operation or after some use doesn't mean it's good. Put the battery on a charger. If it shows 12.7 V or something higher, it's holding a high surface plate charge and as soon as you use it, it will drop back to a normal reading of 12.3-12.5V without a load. This is an indication of a bad battery or what the computer considers a bad battery. Though I can't rule out that you may have a bad temp sensor or thermostat, if the car wasn't running very long, there's no way it should get hot that quickly. Did you also check the oil? Check around under the car for any leaks? (coolant or oil) Also the fan will come on steady if you overfill the coolant as well. Hope that helps.
MercZero11 hey update - Battery now fully charged, after a long struggle and consulting with many work shop finally the fan’s resistant was at fault. For $350 bucks got it fixed.
MercZero11 hey update - Battery now fully charged, after a long struggle and consulting with many work shop finally the fan’s resistant was at fault. For $350 bucks got it fixed.
Im not sure if i understand. I have same problem my fan is runnign randomly when the engine is off. My w212 is in third service now and nobody can find the solution why :(
@@TeamKiller06 it was complicated to find where is that problem and not every mechanic was able to find it. My electro specialist found short-circuit on one of ecu called SAM.
@@zmizni Thanks for the reply. So did you replaced the entire ECU/SAM or the electro-specialist soldered a new component on your sam? I have the same issue. It drained completely my battery in one night. Did you noticed other symptoms when you had this problem? Thank you!
It does make sense, watch the video again. The computer has a sense circuit, if any one parameter of the battery gets out of spec, it kills the battery so you'll replace it.
Hi. I have a W204 2009 C180 ( 1.6 engine) petrol bought last year with 97k miles in the UK. Few months ago one day, turned on rhe AC and the light flashed for a while. Soon after that, since that moment, the fan switches on high few moments after I start the car, every single time and turns off when I turn off the car. I had the AC gas refilled yesterday and fan still doing same thing. Any idea what could be? Im glad you figured yours out:D
I'm fairly new to the German car world so I may not be the best person to ask but here are my thoughts: First, are we talking the radiator fan or the cabin air fan? Plug in a scan tool and see if there are any error codes, that's the first and easiest thing to do. Did the you or the shop reset any error codes related to the A/C being low or out of coolant? There could be a senor sending a false temp reading causing the computer to think the fan needs to ramp up. Was the system cleared of any moisture? Also, I've read that there are methods to reset the climate control panel itself but I'm not sure if they work for the W204. I'd be very suspicious of a malfunctioning temperature sensor but it's hard to say. If you have any other details or find the solution, I'd be happy to hear about it.
MercZero11 Hi. Just received today a Carsoft i980 diag tool. I am gonna plug it in tommorow and see with what error codes is coming. I also have right rear door s lock mechanism playing up and does not lock with central locking or unlock at times. So I have two issues at the moment. Ill come back to give you an upadate. I have read so much on forums and seems to be a common problem with Mercedes both issues that I have. Thank you for your time. I shall keep you updated.
I had to recharge my A/C system myself and I was thinking about this some more. Your A/C system might be overfilled. Listen carefully to hear if the the compressor is clutching in and out at short intervals. Nearly all modern cars have TXV vales that regulate the low side pressure, so if that's all you are monitoring, you could easily overfill the system. All the extra refrigerant would end up on the high pressure side. That would in turn cause heat build up, as well as excess pressure on the compressor, and trigger the fan to ramp up. Just a thought, there could be many reasons but, since you mentioned you just had it filled then the problem started, that's what I would suspect.
MercZero11 Few months ago the A C button light flashed when I pressed it on. Soon after that I could heart the fan on. 2 days ago I had it refilled at a well know garage. They bleed the system and refilled it. So the problem was there already. I havent managed to put my diagnostic machine on yet but tommmorow Im off and Ill come back with the codes. Thank you for taking time to answer.
MercZero11 Checked the car with a Carsoft i980. It only shows my right rear door issues( plays up when I use central locking) but nothing related to A C ( no error codes present). I might have to take it somewhere else for further checks. What do you think?
Back in the days, if you call Mercedes road side service, they can swap out your battery and has the best price.. They discontinue that service. sucks. Just a note, go with mercedes batteries. The mercedes are picky with voltage..
Don't go replacing your battery expecting to fix a cooling fan issue and here is why. By the way, epic fail by MB to have the cooling fan kick on when the ECU sees a low voltage situation. I just replaced the battery in my C280 because someone put the wrong size battery in it. I opted for the factory replacement since no one around here had the correct size, physical size , none were long enough to use the battery hold down clamp on the end. You never want a battery sliding around under the hood , ever. Anyways $180 at the dealer for the battery , installed it my self. Right after I installed the new battery I realized the fan was kicking on when the car would sit for a while, then in would cycle on and off , then it would randomly just stay on full high speed all of which happened with engine off and key out of ignition , like it has a mind of its own. At the time I thought it had something to do with the key fob issues I was having so I just disconnected the battery , then had to have car towed to dealer for the key fob issue which is another long post all together, lol. Anyways I have my key fob issue squared away , I have a new battery from the dealer in the car AND the cooling fan is still kicking on at random times. Sometimes it will stay on , sometimes it will pulse real fast on and off , sometimes it will stay off. From all the reading I have done so far there is a 90% chance its the ECU . I like this C280 but MB just over engineered the crap out of the electronics making it difficult even for the most experienced do it yourselfers to diagnose and repair so you have to go back to the dealer and spend big bucks to have it repaired.
Thanks for this! Had the exact same problem. Got to my car after work, battery completely dead. Very strange, as I had recharged it, just as a precaution, a few days ago, as some little electrical niggles had started. Thankfully the lady who had parked in front of me got to her car at the same time and let me know the fan had been running on high when she got there. Obviously what had drained the battery... I tried jump-starting the car and as soon as it had enough charge, the fan came on again and drained all the charge - so much so that I couldn't jump start it. Disconnected the fan, jump started the car and reconnected the fan so I could drive home. Have now disconnected the battery and put it on a recond-charge. Been 12 hours, still not fully charged - think it's time for a new one! Thanks for saving me a lot of head-scratching!!
Hey guys. In my case the block heater caused the problem.
I live in Canada and I have to plug it to keep it warm when the temperature is too cold. I put a trikle charger (Noco Genius 2G) that means the battery is always on the right voltage.
I conected together under the hood with the block heater.
But.... I forgot to put a timer to turn them on and off every 15 or 30 minutes. My block heater was working and overheated my coolant for 5 days nonstop.
The sensor was detecting 100 degrees for that time.
I solved uplugging it for 2 or 3 days and letting the temperature dropps to cero degrees.
I started it again with the coolant cold and the problem was solved.
Sometimes you fix the issue not because you are replacing the battery... You are fixing the problem cause you are reseting the computer unplugging the battery for at least one minute.
It was my experience.
Just wanted to say thank you. This exact thing happened to my daughters C300 yesterday. I got a new AGM battery today and the fan stopped running when shutoff.
I want to say thank you.., That’s what is happening to my car right now I’ve been trying to figure it out until I watch your video
I had EXACTLY the same problem with my ML430. It's one of those strange things. It makes absolutely no sense. The battery that I take out of the ML gets put into one of the other cars and gives a few more years of service (This has happened more than once). Once the ML has a new battery the fan works and powers down and a few more gremlins stop acting up (at night the radio backlight doesn't switch on sometimes). I even tried to put a new battery from one of the other cars that is underspecked and it also gave me the glitches. I tried with a 8A charger connected and the battery fully charged and it still glitched. The only solution even though it makes ABSOLUTELY NO SENSE is to replace the battery with a good quality NEW battery. The battery drain issues also stop with the new battery. I have also noticed that it happens after the battery has been discharged once in its life where it has insufficient power to start the engine just once. After recharging it appears to be okay but it isn't.
My Vito115 does the same thing. Once the battery reaches a certain age the van drains the battery (via the computer fam) until a new one is installed.
My SL320 has a marvelous feature. when the battery goes low it disconnects thereby preventing battery damage. Just a few minutes of charging and the car is good to go.
My 280SL is still the most reliable car ever nearly no electronics.
Sounds exactly right. Thanks for the overview. Most people don't realize there are more parameters to battery than just storing 12V. The sense circuit is just a little too sensitive. I get the logic behind the car killing the battery so you'll replace it but, in practice, it could leave you stuck. Because even my little booster pack I keep in the trunk would just cause the fan to come on full blast, you'd have to unplug the fan header, start the car then plug it back in with the car running. Not a great situation.
thus is NOT a feature, it is a bug of the battery Management. Fear not the newer Benz still retain this battery drain.
Tons of heavy duty 1st tier AGM batteries get discarded for no good reason.
The issue is tied with the reading of battery sensor over the CAN-BUS or lack of communication with it through "gateway module"....
Use "worskop menu" to display batt. voltage on the dashboard while driving... witness what is happening !!
This was a very clear and helpful video!
I have a similar issue on 2009 ML320. It's a grounding problem with the blower motor, which is costly to replace. Under the glove compartment take down the panel and you will see a connector to the blower motor. I just wired it directly to manually turn on/off through a switch.
Copied from another thread
You had an internal crack or break at the post, on your battery.. unique issue. Thats caused by hitting the post with excessive impact or overtightening the battery clamps, causing the battery post to flex and resulting damage.
I'm having a similar problem right now.(2011 c300) I left my lights on and the battery was dead in the morning, now once I charge it, it works but then the fan continues to run, which I think is draining it, so then it dies again. Took it to where I bought it, they think its a module or a sensor, nobody seems to want to listen to my suggestion about the fan running because of the bad battery. They have me bringing to their Mercedes specialist for a second opinion. I called the dealer they want $165 and hour just to diagnose.
Hi Melissa, sorry to hear you're having problems. Let's see if we can narrow it down. Do you know how old the battery is? And did you measure the voltage in the morning when you realized it was dead?
From what you've said so far, it's possible to ruin battery by discharging it down to a really low level. Which leaving your lights on could do. Especially if the battery is a little older. It reduces it's capacity to hold charge and the computer on these cars is very sensitive to a battery not being in spec. I'd start by load testing the battery, looking at the voltage before and after a charge cycle as well. Even if it tests ok, I'd see if I could get another battery to even hook up temporarily and see what it does. If the battery is anywhere near 5 years old, I'd just replace it. If a scan has already been done with a Mercedes specific scan tool, it's unlikely the star diagnostics would be able to tell you anything more. It is possible for a fan module or ecu, or engine temp sensor to go bad but there would more than likely be an error code.
Also make sure the battery clamps are secure and free of corrosion.
The battery is actually only 11 months old, which is why I thought one night with the lights on wouldn't be that big a deal. Unfortunately I don't have a voltage checker (that may be little out of my skill set) luckily they are sending it to their Mercedes mechanic for me who isn't going to charge to diagnose. I just like to be as educated as possible. It's weird because even though the lights were turned on (not auto) they were not actually on (like shining light) My car does this strange thing when it rains, where the "Auto Light Inoperative" warning comes on and the wipers don't work, this was happening the other day, which was why I turned the switch to on. This is also something no one has been able to figure out. Have you heard or had that issue?
Oh ok, it could still be a bad battery but with that information it sounds like the issue is elsewhere. If you're not comfortable with a multimeter or load tester, best leave it to a mechanic you trust. I haven't heard of that issue specifically. When it comes to diagnostics, multiple things happening at once are rarely a coincidence. I could guess at what the issue is all night but what you need are some initial measurements so you can break the problem down to smaller levels until you isolate it. With any problem, there can be many things that would cause it. I hope you can get it figured out and report back. I'd love to hear what you or your mechanic find.
So I just heard back from the mechanic (literally had the car this whole time) and they said that the satellite radio, which I don't use or even knew I had, was continually running and that was what was draining the battery and causing the fan to run. So since I don't use it the fix is going to be to just disconnect it. They are charging me $390 for the diagnostic and fix, which I guess is better than the dealer would have. But still a little frustrating. Not sure what I think at this point, any thoughts?!?
My car (2008 c300) just did the exact same thing tonight. I noticed it turned on without the key anywhere near the car. when i unlocked / locked the car, the fan would shut off for a minute; then turn right back on. Did this several times before I disconnected the battery. Ill have to deal with it tomorrow night when the stores are open. I noticed its the original battery as well. Hoping thats my issue.
On a side note, I will have a video posted tomorrow of s funky thing my nav screen is doing. If you wouldn't mind taking a look and seeing what you think, that would be great! it has a mind of its own, that's for sure!
I can't guarantee it but, it could likely be a bad battery. The computer is always monitoring it and if it falls out of spec it will start killing it by running the fan so you'll replace it. And it's not unlikely that a bad battery wouldn't cause other issues. The other thing to check, with the car on, does the temperature gauge respond normally? (show cold when first starting in the morning then gradually come to operating temp and stay above 80) If not, it could be a temperature sensor. It's also possible that the fan control module is bad. Given what you've told me, these are less likely. If it's the original battery, change it, it's old enough you'll start having problems anyway.
And I will take a look at your video for sure. Good luck!
What happened? Did it solve the problem after changing the battery?
I have the exact same issue for 2 nights in a row. The car is currently in a service, and i've told the guys not to replace the battery in order not to kill a brand new battery, but to try to find the problem, and couple of days after they're still unable to find where the problem might be. I'm a bit concerned about the ECU as it is the most expensive opiton in that case, but still, I might ask them to try with a brand new, quality battery. Almost forgot to mention, they tried with brand new fan kit (including the fan module and everyting) but the car have had the same issues. I've also having the fan on full speed even when the car is on, and once I turn the ignition off, and wait for a couple of hours, the fan ramps up and kills the battery. My current battery is about 4y old, could you please share any thoughts on this, and whether you managed to fix the problem by replacing the either battery or ECU?
hey man im having the same problem. Sometimes the fan would turn on after shutting the car off, but it would only come on for a quick few secs, than shut off. Than sometimes my fan would work during idling and than it wouldnt work and would overheat my car... Than it would fully work with ac and heat on. I just changed the battery and it still the same and i changed the coolant thermosttat and still the same.
what was your resolution im having the same problem, just bought a new battery. The fan is draining my battery.
I have a 2002 E320 that has a similar problem. I’m thinking because I have a significant battery drain problem, I’m sure it’s the radio that’s causing the drain. I jump started the car wash he other day and the blower fan came on without being turned on . I switched the car off and it continued to run full blast! Could this be from jump starting car and the computer going haywire?
Thank you very much for your help I really appreciate your video and the way you explain things to be thank you
I have this issue right now !! Great video !!
How you got it fixed ? I am facing the same issue now.
hi i have the same issue right now
@@nimeshobha
I have a same issue with my fan
Some days after turn off engine fan will go fast and stop suddenly, after 20 to 30 min unlock my car it will start again in full speed and off, when car is running temp wil go to 100 c suddenly drop of to 80 c and sign of tempture will turn on and off, after turn off the car for 10 min every thing will run normal again in some days in traffic temp raise near over heating in 120 c i checked fan not working
Maybe you can help me, I know what caused my problem. I had been looking at my fuses to try to disable the car alarm that kept going off randomly. I did not even touch the fuses as I figured I would later that day and my big mistake was leaving the fuse cover off since I knew I would be back later on. The problem is I went for gas and figured why not get a car wash. I did and as I came out of the wash I heard the radiator fan louder than usual. I pulled off to the side of the car wash and turned off the engine and then the fan came back on .... I pulled out the key and it still stayed on. Then I opened the hood and I saw that I had left the fuse box cover off and looked closer and I saw some small drops of water on the fuses. Murphy's Law. I left the cover off and then got a car wash and water had somehow sprayed under the bonnet. A bad coincidence. I dried it off as best I could. The fan stayed on. I drove it home and it stayed on even without the key. Right now I have the negative terminal off the battery to stop the fan. I will readdress the problem in the daylight tomorrow. Any thoughts ?
If you're convinced the problem is in the fuse box, it will likely be fixed once the excess water dries up.
A couple drops of water in the fuse box shouldn't be a big deal but if you're not sure how much got in, it needs to be flushed from around any contacts to prevent corrosion. You may need to pull some or all the fuses and relays. Either way, isopropyl alcohol (over 90% if you can get it) and slowly pour it over the whole area of contacts, there should be a drain in the box and this will dilute and flush most of the water. You don't have to use the whole bottle. Next step is to get a hair dryer on a lightly warm setting and heat the whole interior of the fuse box so any other moisture and alcohol will evaporate off. Be careful!
Was the engine temperature gauge in the normal range? You could have a bad thermostat. It is also possible for the fan control module to go bad.
Also check your battery is good and the cables are securely fastened and no excessive corrosion on the terminals or cables. Coincidences do happen sometimes so don't assume anything. Good luck!
@@merczero1184 The temperature was not abnormal ... night time .... cool weather. I am convinced it is because I left the cover off before I did the car wash ... it all occurred right after the car wash and it was zero problem before. I sure hope that I did not cause a short. Thanks ... will do all that you advise !
@@funguy4utube is it resolved ? I am facing the same issue with my MB GLK 350 . Please advise.
@@nimeshobha I wrote you a long detailed answer and before I sent it my cell died and the response vaporized. So here goes once again. I felt the problem was caused by the water getting into my fusebox, so in the morning I reconnected the battery, and I sprayed the open fuse box with WD-40 and I left the cover off and drove for around ten minutes thinking the hot air blowing around would dry out the fuse area. It did. the problem cured itself. As for the pulling the fuse that competes the circuit for the alarm ..... I have yet to do that. It seems to be one of two 7.5 amp brown fuse in the engine fuse box. The alarm going off .... which was the root of my problem ... has only happened a few times since. I do not set the alarm by locking the car and thereby it does not go off. If I do set the alarm and IF it does go off on it's own .... I go out to the car and put the key in and it goes off. Obviously it is not safe to leave the key in so I put my other car behind the Merc to block the driveway ....... I know that once I have the time I can test pull the brown fuses and determine which one kills the alarm horn.
@@funguy4utube Dude this is 100% exact same issue that happened to me with my 2005 CLK-320. First my alarm messed up, pulled 7.5amp brown fuse in rear SAM. Then i was messing with front cover, left it off drove to work and it rained. Needed a jumpstart to get home, and suspected that was the issue ! This is crazy hahaha.
use the "secret workshop menu" to display batt voltage on the dashboarf while driving - You'll see how the computer wants to charge your battery !
Max 14.9v into AGM while cold
Above 12.6v it is charging ok
Below 12.4v it's draining power
Below 11.9v dont drive too far!
"Whorkshop menu" is invoked prior to engine start sequence
👍🏻
That's a good tip. You can also monitor it with any number of OBDII readers.
Great review, thank you!
We're in green wood are you located
I’m having a similar issue but my car battery got changed and now it still says transmission not in park risk of rolling away and anti theft enabled and vehicular is immobile
Sounds like you need to do some diagnostics. If all those problems happened at or around the same time, assume they are all from the same source until proven otherwise. If you're not up to the task of hunting down electrical problems, bad sensors, switches, connectors, wiring etc. just save yourself the frustration and take it to a garage.
Guys my problem is little diff, w204, c200 (petrol) 2009, today i had a engine heat signal so i quickly changed coolent (it was low), within few seconds after the warning sign i stopped and put coolent.
Now my fan keeps on running, even after switching my engine off. I waited for 20 minutes still it was running. Finally disconnected the battery. Hope changing battery will help.
What does the temperature gauge read? How long was the car running before you got the heat warning?
MercZero11 hey, once the temperature indicators came I immediately stopped my car, may be 5 meters or 10, coz i just went to get some drinks near my house. (Maximum 1.5 miles the car has run post which i saw the indicator ) the car is hardly used. Now once i stopped at put water first the temps gauge never went up neither i saw any warning. Now i just asked the battery company to take a dif battery and check but same issue. My battery volt 12.25 new battery volt 12.55. What to do :(
@@james2k00 Unless the battery was drained to a really low voltage and/or sat for a long time , I'd try charging it first. Possibly even cycling it to full charge then discharge a few times. As I say in the video, normal battery voltage reading during operation or after some use doesn't mean it's good. Put the battery on a charger. If it shows 12.7 V or something higher, it's holding a high surface plate charge and as soon as you use it, it will drop back to a normal reading of 12.3-12.5V without a load. This is an indication of a bad battery or what the computer considers a bad battery. Though I can't rule out that you may have a bad temp sensor or thermostat, if the car wasn't running very long, there's no way it should get hot that quickly. Did you also check the oil? Check around under the car for any leaks? (coolant or oil) Also the fan will come on steady if you overfill the coolant as well. Hope that helps.
MercZero11 hey update - Battery now fully charged, after a long struggle and consulting with many work shop finally the fan’s resistant was at fault. For $350 bucks got it fixed.
MercZero11 hey update - Battery now fully charged, after a long struggle and consulting with many work shop finally the fan’s resistant was at fault. For $350 bucks got it fixed.
Thsnk you today I had the same problem thanks to your video it was my battery thanks
Im not sure if i understand. I have same problem my fan is runnign randomly when the engine is off. My w212 is in third service now and nobody can find the solution why :(
I've got the same problem today on my w212. Did you find the problem? I don't think it's battery, because my battery is brand new.
@@TeamKiller06 it was complicated to find where is that problem and not every mechanic was able to find it. My electro specialist found short-circuit on one of ecu called SAM.
@@zmizni Thanks for the reply. So did you replaced the entire ECU/SAM or the electro-specialist soldered a new component on your sam? I have the same issue. It drained completely my battery in one night. Did you noticed other symptoms when you had this problem?
Thank you!
How can it be the battery??? That makes zero sense... lol
It does make sense, watch the video again. The computer has a sense circuit, if any one parameter of the battery gets out of spec, it kills the battery so you'll replace it.
Replaced my battery and it’s still doing it,
That sign is a sign of BAD ECU UNFORTUNATELY AS OT THE MOST EXPENSIVE PART TO REPLACE AND ITS NOT YOUR BATTERY
Untrue, could be sensor, or fan controller..etc. ECU is NOT a "usual" problem
Hi. I have a W204 2009 C180 ( 1.6 engine) petrol bought last year with 97k miles in the UK. Few months ago one day, turned on rhe AC and the light flashed for a while. Soon after that, since that moment, the fan switches on high few moments after I start the car, every single time and turns off when I turn off the car. I had the AC gas refilled yesterday and fan still doing same thing. Any idea what could be? Im glad you figured yours out:D
I'm fairly new to the German car world so I may not be the best person to ask but here are my thoughts: First, are we talking the radiator fan or the cabin air fan? Plug in a scan tool and see if there are any error codes, that's the first and easiest thing to do. Did the you or the shop reset any error codes related to the A/C being low or out of coolant? There could be a senor sending a false temp reading causing the computer to think the fan needs to ramp up. Was the system cleared of any moisture? Also, I've read that there are methods to reset the climate control panel itself but I'm not sure if they work for the W204. I'd be very suspicious of a malfunctioning temperature sensor but it's hard to say. If you have any other details or find the solution, I'd be happy to hear about it.
MercZero11 Hi. Just received today a Carsoft i980 diag tool. I am gonna plug it in tommorow and see with what error codes is coming. I also have right rear door s lock mechanism playing up and does not lock with central locking or unlock at times. So I have two issues at the moment. Ill come back to give you an upadate. I have read so much on forums and seems to be a common problem with Mercedes both issues that I have. Thank you for your time. I shall keep you updated.
I had to recharge my A/C system myself and I was thinking about this some more. Your A/C system might be overfilled. Listen carefully to hear if the the compressor is clutching in and out at short intervals. Nearly all modern cars have TXV vales that regulate the low side pressure, so if that's all you are monitoring, you could easily overfill the system. All the extra refrigerant would end up on the high pressure side. That would in turn cause heat build up, as well as excess pressure on the compressor, and trigger the fan to ramp up. Just a thought, there could be many reasons but, since you mentioned you just had it filled then the problem started, that's what I would suspect.
MercZero11 Few months ago the A C button light flashed when I pressed it on. Soon after that I could heart the fan on. 2 days ago I had it refilled at a well know garage. They bleed the system and refilled it. So the problem was there already. I havent managed to put my diagnostic machine on yet but tommmorow Im off and Ill come back with the codes. Thank you for taking time to answer.
MercZero11 Checked the car with a Carsoft i980. It only shows my right rear door issues( plays up when I use central locking) but nothing related to A C ( no error codes present). I might have to take it somewhere else for further checks. What do you think?
Back in the days, if you call Mercedes road side service, they can swap out your battery and has the best price.. They discontinue that service. sucks. Just a note, go with mercedes batteries. The mercedes are picky with voltage..
Mercedes doesn't make batteries. Or tires. Or oil. Or windshield wipers. Buying those things from Mercedes is silly.
no reason disclose in this vedio .unfinished