Fixing erratic heat issues on W126 S class Benz 300SDL 420SEL 560SEL 300SE W124
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- Опубліковано 23 бер 2018
- Here is a comprehensive check list of what and where to check for trouble in your heating and cooling system. Learn how to inspect functionality of interior heat sensor, mono valve, CCU climate control unit, interior temp sensor blower, and the auxiliary cooling water pump.
In the video you will also find the part number of the correct MB mono valve insert A0008350644. Do not use the cheap online replacements - they simply do not work correctly.
In the event you have a genuine mono valve that no longer works, there is now a repair kit that helps you replace the rubber parts. Here is the link: www.pelicanparts.com/More_Inf...
The following genuine BMW mono valve insert is identical to the Benz part A0008350644: Genuine BMW E24 E28 E32 E34 Mono Valve Heater Solenoid Valve OEM part number 64118390132. It costs a pretty Penny, but this has a greater chance fixing your erratic heat issues than buying the cheap online parts store inserts.
Update: This part number now also no longer seems to be available.
The controller part number that was used here is 126-830-05-85. - Навчання та стиль
GLAD I FOUND YOU CANT BEAT OLD MERCEDES HAD TEN DIFFERNT KINDS STILL LEARNING
And there is plenty to learn.
Hi Ralph
Thanks for another useful video. It’s funny how we have to learn everything by hard way , but thanks to you , you make all work which these old Mercedeses requires a bit easier by posting very useful videos. Thank you and I look forward to next useful video. Take care,Patrik.
Thank you so much. The best of luck to you!
Very helpful!! I appreciate you making this video. Working on my car now, just got another mono valve from another SDL have a feeling that’s my problem. Thanks again!
Thanks and good luck!
Best explanation I have seen on how the heater works. I have been fighting mine for several years and this gives me hope.
Thank you and the best of luck!
Bravo sir, best video I have seen to date on where to start diagnosing heat issues with w126.
Thank you Taylor!
Another great video with hard to find information. Thank you.
Thank you. Glad it helped.
Happy knew year cobba, I really enjoy your vids matey,good luck
Thanks, my man. Happy New Year to you also.
Thanks a lot, that’s very helpful. Looking forward to more videos on the w126
G Maximillian Thanks!
:)
Hello Ralph,
I came across this video searching for other stuff. I watched till the end because of your presentation.
So clear and straight forward, anyone should be able to follow.
By the way, your continues smile and the wide suspenders made me feel like I was in Bavaria getting ready for October fest. 😀
Thank you,, Sir.
Sorry, Is it Ralph or Ralf?
@@marekhabel2493 No worries. It is Ralf
thankyou for reply onl one wiper works now LIKE YOU SAID EVRYTHING ELSE BREAKS TRANSMISSION STICK CRUMBLED IN MY HAND LOL
There is always something to fix.
Excellent information Ralph !!
Thanks for sharing your findings through much misery.
I was replacing the right side cam today and noticed the mono-valve since I had that section of firewall out. I saw the coolant lines running to it and wondered if that was the heating issue my uncle told me about. I will try your suggestions.
I couldn't really find any information on the heating system for a '85 w126 SEL so Thanks again for your contribution. Looking forward to more videos.
Note Nowe Thanks and good luck!
:0
Great tips Ralph!
Thank you Sir.
It's very helpful, thank you
Glad it helped.
Thanks for the tips on the climate control of the w126. Mine is the gen 1, 500 sel, but certain the information will give me what I need, as I'm trying to preserve what is left of a fine marque and model. Take care.
Hi Murray. There is a lot of commonality between the systems as far as the overall logic is concerned. The usual culprits like the mono valve, CCU, vacuum actuators, vacuum leaks, in car temp sensor, heat and AC evap temp sensors, engine temp sensor, and finally the coolant recirc pump are all things that you can find a lot of info about on MB forums. Good luck saving your Benz!
@@straybenzes All you've mentioned will undoubtedly be of benefit since 1985 Shop Manuals are sight unseen these days. My Father was always buzzing about the 1950's Benz's that he saw in Berlin at that time. I'm more of family car sort, than a coupe or roadsters type, and always admired German Cars, having owned Beetles, and BMW's for their engineering excellence, with only my 64' Ford Galaxie having come close to Teutonic perfection, and only for a short while between 41' and the 71' being Ford's hallmark years. I adore my W126, but have huge obstacles to overcome with it. Thank you for your time and efforts my friend.
@@murraykriner9425 I am with you in though and spirit. The best of luck to you.
Gracias amigo....., for share your knowledge .
Thank you!
very helpful video!! i have the same problem with my 420sel w126 86" when the car is stoped on idle it have heat but when you push the gas pedal or start run the heat its gone like magic. i try to fix it myself with change the mono valve and ccu unit but i wasnt know abut the interior heat sensor...so before that video i was rady to remove the heater radiator but now i will try this thanx man you help very much...keep it!!! hello from greece
Good luck!
@@straybenzes Finnaly the problem was the motor from interior sensor...was a big suprise when i start looking for the motor due to no vacum from the interior sensor and guess....nowhere motor!!! just the plug and motor nowhere... luckly i find one and its ok now...maybe someone forget it or it was broke i dont know.. just thank you ralph realy!!
nasos krikos I am glad you found the problem
Heard you say often that getting authentic Benz parts was an absolute necessity. Already knew about the Mono Valve, and even the auxiliary pump against the firewall (what a place to put it), but the interior sensor and electric fan really floored me. At least I know were I'm heading when I get to the HVAC repairs. Thanks so much my friend. Very best wishes, Ralph.
Thanks and good luck fixing your classic Benz.
@@straybenzes your such a joy to have around. I hope that all other's know how really fortunate they are to have you involved in their efforts. Thank you Ralph.
@@murraykriner9425 Aww! Thank you, Sir.
@@straybenzes you are most generously welcome my friend.
@@murraykriner9425 :)
Excellent guide!
Eduardo Uruena Thanks!
:)
THANKS
Welcome
Thank you sir you rock
Thanks!
You’re a pro I wish I could do everything like you unfortunately no that’s why I am on this watching thanks you’ve been a big help I have one problem I’m trying to replace my bulb on my Mercedes 1987SDL for the vents in the center I do not know how to remove the vents To replace the lightbulbs for the switches right under the vents they have little dots I think that light up please help PS do the switches such as the antenna The recycle rear light all those switches have their own separate bulbs built-in lightbulb in rear passenger switch is not lit up and some of the front counsel
I may do a video soon about that one light bulb. You need to remove the ashtray, Radio, and the climate controller. There is only one light bulb that is connected to the switches in the upper center console with fiber optic cable. Sometimes the cables fall out the back of the switches etc.It sounds difficult, but it is not.
Much good information Ralph I did not really know about the inside temp. sensor and the fan for it and the auxiliary pump. Have to wonder how they can sell those after market mono valves if they do not work? That should be outlawed. You posted a lot of useful information. Thank-You
The mono valve insert not being available anymore from MB is just sad. The cheap copies serve only one purpose: save the old insert and only replace the rubber parts with the parts off of the cheap knock off.
I BOUGHT HE CLIPS MOTORS ALL WORK
Cool.
great!! thanks!! BTW what is the I.D. of the hoses to heater core? For temporary bypass of duo-ventil...
I unfortunately do not have the part numbers handy. Any of the usual online parts companies like Peach Parts, etc can help you out with those hoses. All the best.
Awesome video Ralph! Do you live in Canada by chance? Cheers Sven from Edmonton
Cara Peters Sorry, but no. Pennsylvania USA. All the best!
:)
Huh, guess that explains why the replacement monovalve I put in a few years ago never actually worked and actually made it worse lol.
Yup, that was exactly what happened to me except someone had already swapped out the original one before me. It is not the greatest situation for certain.
Bro I love how you reply fast how easy is it to remover the rear bumper one of my clips snapped I’m try to diy repair it but I have to take the bumper off and I can’t find a video on how to
I do y’all the work on my own car but just trying to make sure
Thanks for the request. Let me see when we can do that one.
@@Devan_Bolin The best of luck to you in the meantime.
Is there a cabin filter on the 1988 420SEL? also how do you recirculate air when its hot out with the air on.
There is no cabin filter on W126 cars. There is a recirc switch on the upper center console with arrows in a circle. That only works though if the vacuum pods are still in good shape and the vacuum level is as per spec.
Thank you so much for your video on the Mercedes climate control. I just tested my temperature sensor for air flow as you show and I must have a problem with the temperature sensor fan. You mentioned that there are videos out there that show how to fix that fan, but I can't seem to be able to find one. Can you suggest a video to help me fix that fan? Also, what is the actual name and/or part number of that fan, because I can't find it in any of my Mercedes parts catalogs? Thank you so much.
Hi John. It is not uncommon for this fan to lock up after years of service or just from sitting too long. It is the cabin temp sensor blower and the part number is 000 830 19 08. Here are two places where you can find it: www.ebay.com/itm/For-Mercedes-W124-W126-HVAC-Temperature-Sensor-Motor-Blower-Fan-for-Cabin-Air/151994812713?epid=1923570211&hash=item236398c929:g:oc4AAOSwnTxZbawV and here: www.partsgeek.com/gbproducts/DC/6125-05818332.html?DN&PartsGeek+Google+Base&+Mercedes+190E+Blower+Motor+Genuine+000+830+19+08+84-93+Mercedes+Blower+Motor+1990+1991&fp=pp&gbm=a&PartsGeek+Google+Basecid=6774379819&aid=79287199093&keyword=829684093649%3A%3Apla-829684093649&kid=829684093649&gclid=CjwKCAiAjMHwBRAVEiwAzdLWGLTyqZ0rVX7VVUNBoEbgQjfg3kajSixs96hzH3JKASNqbyrRj9bwcxoCxEgQAvD_BwE. You are correct, there are not too many pieces of advice of how to remove it. I will put it on my list to cover. Thanks!
With LH drive cars the blowers sits on the passenger side. You need to remove the lower A column cover panel on the right side in the footwell and the under dash cover under the glove box or passenger air bag. The blower sits way up under the right lower dash and is held in place with a very brittle piece of foam. Carefully disconnect plug and hose. Do not tug on the tube too hard. Re-assemble in reverse order. It is not difficult, but you will need a good work light and some patience to get to the blower. Good luck.
@@straybenzes You are so helpful, I can't tell you how much I appreciate it. I failed to tell you that the Mercedes I have is a 1985 380SE. I have a small collection of US classic cars and trucks from the 50s and 60s that I have rebuilt over the years, but this Mercedes just fascinates me. The engine is so powerful and that generation of Mercedes is made up of so many advancements for "sports sedans" that set the stage for modern day cars. Yet, it is really complicated compared to the other old vehicles I have rebuilt. I just rebuilt the undercarriage and simply replacing the rear shocks was an experience all to itself!
@@johnmitola8815 That is a great post. Thank you for sharing!
what is the correct part number for the HVAC Controller? I might have missed it, but I've rewatched this thing a couple times.
Hi there;
The part number that was used here is 126-830-05-85. Good luck!
@@straybenzes thanks, awesome
@@thedirtlifesupreame Glad it helped.
Hi I have a .86 420sel. The climate control is erratic as well. The ignition switch is on position 1 and it comes on and off. I tried to turn it off then it would come on by itself. The same thing happens when I'm driving as well.
Yeah, that is a sign of a bad CCU, unfortunately. Make sure that your aux water pump is not locked up causing an overload in the CCU. That will cause the CCU to get fried. Another frequent issue is the cabin temp sensor fan seizing - that can cause for the main fan speed to go up and down RPM wise. Good luck! Make sure that you get the exact CCU part number that you have installed there (assuming it is the original). Using an incorrect p/n unit can also cause erratic behavior.
Any chance of getting more info on the the interior sensor and electric fan? I tried mine and it doesn't work and don't know where to start to get the parts. Thanks for the info.
The interior sensor is very rarely the issue. The little cabin air sensor blower is more so an issue. Fortunately it is still readily available brand new from e.g. this vendor www.pelicanparts.com/More_Info/0008301908.htm?pn=000-830-19-08-MBZ I will add your request to my requested video list
@@straybenzes That's excellent Stray, Pelican have the part. I was going to order the blower and thought I would buy the mono valve as well but they don't have one. Where did you get yours?
I tried to locate the mono valve insert. The BMW part you list is also showing "discontinued - no longer available"
Yeah, I am afraid the door is closing on us and only the cheap and typically non working Chinese made ones will be available anymore. I have seen and heard something about a VW part being available that supposedly will work, but I actually have not found a part number, web site, etc. I will update the video description in the event that I do find that information.
Apparently a good aftermarket mono valve is now available that works, not a cheap Chinese one. Its called a Klima mono valve, a direct replacement of whole unit. Correct me if I'm wrong on this. 👍
@@kevinford6420 Is this the one that you are referring to? klimakit.com/product/monovalve-and-coolant-circulator-pump-eliminator-upgrade-kit/
Ralf I recently picked up an 87 560SL for my wife that has intermittent heat. One time you run the car its great the next stone friggin cold. Replaced the mono valve with an aftermarket, burped the system same issue. Thanks to your advice I bought the original Mercedes one tonight from Pelican Parts. I twisted wrenches for ten years on American cars but Ive never seen anything as annoying as these Mercedes systems. I figured by process of elimination I was down to the issue being either a bad aftermarket mono valve or aux water pump. I didn't know about the inner sensor but I'll try to find mine. But TY so much for telling us about the crap mono valve. I THINK you may have saved me a lot more aggravation. Any idea where the INNER sensor/fan IS on the 560SL? TY.
rf396 Thanks for your comment. The 560SL has the cabin temp sensor built in under the dash. It has an annoying foam hose that can deteriorate. Here is a good write up about it. www.benzworld.org/forums/attachment.php?attachmentid=316974&d=1277965272
@@Ralfweiser Sir you have just saved me a TON and I mean a TON of searching for this. Did a cursory one last night but was only finding that diagram. THIS is gold. Congratulations on becoming MY and I am sure MANY guys GO TO GUY for Mercedes questions. Boy is this becoming an education.
Hi again Ralf. I used the file you sent and replaced the hose. Mine was all but liquefied. Im still waiting on the MB mono valve but, Ive noticed two things. the fan in the cabin sensor isnt spinning, it wont pull a piece of paper towel in. Also it seems that no matter what setting I put the climate control buttons one I get air out of the defrost and two outside dash vents nothing from the inside vents that bracket the outside temp gauge . Is this normal? I'm guessing no but again this is like the first day of school again tracking this trouble in a Benz. Any idea HOW the dash comes off so i can see if that fan is jammed vs broken and does it sound to you like the climate control module may be messed up? Thanks in advance for any info you may have..Rick
@@rf396 Hi Rick. That sounds more like the vent flap actuator diaphragms have surrendered. Ever found a Quarter sized paint blemish in your bathroom that shortly thereafter turned into a $3000 Dollar "quick fresh up"? Well, a time consuming and potentially $$$ DYI job is what I believe you are in for. First take out the glove box and follow the sensor air tube to the end. The little blower should be fixable (I am not 100% sure as my database is down right now), but they are still available as a new part. The other rather labor intensive part are the vent flap actuators. They are all vacuum operated and I believe you have 6 of them tucked into places where even calibrated Swiss Army like fingers cannot easily reach them. You can either replace them or repair them with new diaphragms. Only after you fix them and your vac lines would I move on to messing with the CCU. Here is a video I found about taking out the dash. ua-cam.com/video/GfQ8xWkKulM/v-deo.html Buckle up, put the tray table and seat back into the upright position and hold on for an interesting ride.
Ralf...WHy did I KNOW you were going to say something like that? Because I couldnt win the lottery if I had the ONLY ticket. LOL. In anticipation of having to do that I found that vid earlier TY. I'm shocked that by th end of it you dont hear a gunshot and see the body fall. That looks like absolutely NO fun. BUT THIS condition COULD be lived with. This is my wifes car/toy. It only goes out about once a week for short hops and thats it so I think sged be willing to live with it as is for the vent exits. BUT. I still have the heat issue to deal with. I did replace that foam hose behind the glove box. It terminates at the vent assembly just as male hose receiver. the vent for the fan is on top of the dash. Do you know if that face plate can be pried out so I can get to the sensor fan? As small an opening as that IS its the only way I can SEE to even thumb spin the fan to free it up. Or am I not seeing something?
Hello Ralph I have a 92 w201 is it the same thing?
Yes and no. The overall control schematic, CCU, cabin air temp sensor, aux water pump, etc are very similar. The one main difference is that the W201 does not have a heater mono valve. You should have a vacuum actuated control valve instead.
Hello Ralf, I am facing issue, that bottom of the car heats perfectly, but the windshield gets just cold air. This is an issue under 0 degree Celsius. Between 0 and -10, the car can be driven, but under -10 most of the car is completely cold in 10-20 minutes so it is unbearable to drive, even if the bottom is still getting hot air. Any idea what can be the issue?
Hi Julius. This one is mystifying me a little bit. Which button is pushed when this happens? When it is cold I would think that you are in EC mode. I cannot quite follow why the window vent would blow cold air as it is also connected to the same air supply as the bottom. You have the rear center console vent closed, right? That one only blows outside air and would not allow your cabin temp to rise.
Does the window vent blow hot air when you push window defrost? That would at least mean that the vacuum pod and vacuum distributor still works ok. Is this a Gen1 or Gen2 car? They are a little different in how the CCU works.
@@straybenzes Now writing from my memory, I checked it last time in winter two years ago (Because of other reasons I didn't drive the car recently, but I intend to start driving again). I believe I was not in EC mode and I tested with all the buttons, also with Defrost. Generally, I think I use second button from left. Center console was for sure closed. When the car is not moving, the warm air goes to window, but when the car is driving, then the incoming air is somehow stronger than the hot one and in few minutes it becomes completely cold. It is Gen2 car originally from Italy. I already replaced radiator and steering unit without effect.
I HAVE A NEW VOLTAGE REGULATOR CAN JUST SWAP ITOU TWO SCREWS HOLD IN DO I HAVE TO LOSEN ALTERNRTOR
You can just swap out the regulator. Be careful though if you do this without disconnecting the battery (would recommend you do that).
MY WINDOW MOTORS GOOD BU REAR WINDOWSNOT GION UP OR DOWN IS THRE A CIP TO BUY TO PUT ON TRACK?/ HELP
That is either the window regulator, the tracks, or the little plastic guide that will cause this issue. Verify that the motor actually works as you disassemble the regulator out of the door.
From all the “common faults” that affect the 126, it appears that they are not as reliable or well engineered as they are made out to be
There are certain items that turned out to be a not so great engineering idea, e.g. the plastic timing chain guides, biodegradable wiring, etc. Other than that I have to say that long time neglect (because they are so we'll built), unprofessional repairs/ parts, and simply old age are usually the failure root causes of such "common" issues.
What is the correct ecu part number that works in yours? Cuz the one you show on video is the one I have in my 87 300sdl. Thanks
That should be 126 830 05 85. Good luck!
@@straybenzes Thanks, and for the 90/91 350sdl is 126 830 0885
@@alc11803 Thanks!
Ralph, my 300sdl recently has been acting fuuny, the ac fan won't engaged unless I shut off engine and restarted the car,but sometimes it'll work as usual. Would it be the ecu control issue or something else? Thanks
@@alc11803 When you say AC fan which fan do you mean by that? Do you mean the auxiliary fan in front of the condenser / radiator? Or do you mean the cabin air blower?
Hi Ralph, thank you for this video. Do you know the part number for the controller in my 560 SEL from 1986 ? There is no partnumber stamped in the front of the climat controller. The number stamped on the back is: 10 687. I see different part numbers on eBay and don’t know which to buy.
Try either one of these two part numbers. Your original dial should still be in Celsius only the later ones had the dial in F. 126 830 09 85, 1268300985. You can try Programa. Parts off of Ebay are sketchy at best.
Thank you ! You wrote I can try two part numbers. Can you add the other part number because I think there is now only one in your message. There are two numbers but they are the same.
@@tjeerdbijker7350 Oh my goodness. Thank you for pointing that out. I totally thought that the last two digits were different. Sorry, there is indeed only one part number.
@@straybenzes OK ! Thanks Ralph.
@@tjeerdbijker7350 Good luck hunting a unit down for your car.
Hello , I hope you can help me with a recent issue with my blower motor .
I have a 83’ 300SD . I have checked the blower motor itself with the car battery and it turns without any issues, engine bay fuses look good , changed climate control unit with extras I have around and nothing . Blower motor still not working . Do not know what else to check .
Thank you for any assistance you can provide .
Have a blessed day .
If the blower motor runs at full speed when you are applying 12VDC to it then I would focus on the blower motor resistor next. The climate control only sends a speed reference voltage to the resistor and the resistors then regulates blower motor speed using its own power supply voltage (there is too much load on that circuit and the CCU is not designed to handle that amperage directly). That part is the porcupine looking part mounted below/ next to the fan motor. Good luck with the troubleshooting.
@@straybenzes thanks for the información. I found out that the “ blower motor strip fuse in engine bay was blown”
Ordered from Pelican parts along with a new fuse housing kit . The one that is on the car was partially burned when the fused went bad .
Thank you and keep those great videos coming !!
Elvis
@@elvisquezada2113 Love this. I had made the ever so dangerous assumption that you had checked the fuses. You rock. Good luck.
ALSO THE SECONDRY FAN HOW TO TEST IF IT WOTK
If you mean the after 1990 dual fan set then both fans run at the same time and speed. If only one fan is running then the second one not running is either faulty or the wiring is kaputt.
Mercedes source have a aftermarket replacement
Yup, but even uncle Ken's part is just an after market part.
Can you please make video about Temperature Regulator replacement?
Hi Jalil. Please let me know which temperature regulator you mean. Is that the engine thermostat, or perhaps the climate control unit, the mono valve, etc?
Stray Benzes temperature regulator I think it’s located underneath the glovebox
@@Rasulovification Hmm, there is only the fresh air flap and it's vacuum actuators there. Is that what you meant?
‘Temperature Regulator & Blower Control Relay‘ where would I find that?
@@Rasulovification Aha, I got you. Please check out this video: ua-cam.com/video/MyjhVHtxRmw/v-deo.html Check the plug shown in minute 2.38min and with the engine running and in heat or cool put the fan speed control to min speed. The voltage should be 1-1.2VDC after 60 sec. Switch to max fan speed and the voltage should reach 4.7VDC after 60 sec. If that does not happen that means you ACC automatic climate control is toast. Please check your fuses first though and make sure they are all ok. Next check the fan motor after disconnecting the two wires right at the motor. Put a 12VDC power source on it and it should run without making any unusual noises. If you have a working ACC and the fan motor works then this means that your fan voltage regulator needs replacing. Good luck!
HAVE PUT OUT ABOUT OXYGEN SENSORS 126 1989 420SEL DOES IT HAVE 1 OR 2??
1
Hello
My blower comes on when I turn ignition on on high , won’t shut off
Any suggestions how to turn off or control it,
It will not shut off when you turn off the car?
@@straybenzes they blow it inside, keeps running when the car is on, when I turn off the ignition it stops, they suggested it might be fuse number one or fuse number five, I tried removing both of those and the blower inside keeps running
@@abrahamfakhoury873 That is most likely the Blower Control unit N29 that is bad. That is the porcupine-looking thing in the some box as the blower itself.
Mine heat comes on and goes right back out. What could it be
Could be the rubber diaphragm of the mono valve. Can also be due to cabin temp sensor or its blower issues. Finally, it could also be the CCU climate control unit that has gone bad. Hoping this helps.
I think one of my flap actuators is broken or something... Do not know if it is vacuum.
I intend to make a video about how to fix the actuators. Unfortunately, the rubber diaphragms do dry rot and then no longer work. They also cause vacuum system leaks that can cause other issues.
@@straybenzes Thank you for your reply. I will be waiting for that video. in the mean time I have a recirculation switch that will not light up. I thing the 3 vacuum hoses are not connected "1268205110"
@@straybenzes Have you made a video on how to fix these actuators at this time? Just asking...
@@RasSosa Not yet. It is definitely on a growing list of video requests.
1989 4200 SEL 1 OR 2 OXYGEN SENSORS?
1
1989 FAN AUXILLARY
?
Is there a way to bypass the mama valve I just want to heat
Nick Margo Yes there is. All you need to do is to pull the plug off of the mono valve. No voltage= valve fully open. 12v Applied= valve fully closed. This helps troubleshoot a few things. If you have heat at idle but none or little heat at >2000rpm you have the incorrect valve insert installed. If you have little to no heat at idle but nice heat at high rev your aux pump is not working. If the aux pump is fried it usually takes out the CCU (install a 1.5A fuse in the new pump wiring while you are at it).
:)
REPLIES GGRRAATTEEFFUULLLL
You are welcome!