In case you are driving in winter and need some heat in the car before you can make the repair, I discovered that if you just remove the electrical connection to the mono valve assembly you will get constant heat. This worked for me with my 86 560 SEL
You raise a good point. If the mono valve's rubber diaphragm is busted this method will not go into full heat mode. If it is the much more expensive problem for your climate control unit being busted, then pulling the plug on the mono valve will "restore" heat for the winter. It is very warm inside the cabin without opening a window thought. Good luck!
Unfortunately this part isn't available anymore. There are aftermarket parts, but they dont work. Thats sad, because i have a dualvalve and need two of them. Btw. very good video.
There is a band aid fix: If you still have the OEM mono valves and only the rubber diaphragm is kaput then you can buy aftermarket ones and change out only that part. It really comes down to having a good seal whilst retaining the original springs. That is assuming the springs are still ok in the old valves. Good luck!
@@straybenzes Thank you for your advice. Unfortunately the aftermarket parts are also hard to get these days. But after some research i found another way to get original parts. Even if the lift magnets arent available anymore, the whole Duovale is still in stock. This includes 2 lift magnets. i know in US and maybe canada this cars were sold with automatic AC only, so they have monovalves. a MB dealer will tell you the whole duovalve assembly does not fit for your car with monovalve, adter checking your VIN. but of course you can take out the part with the magnetic lifts and the coil and install one of these in a car with monovalve and save the other as spare part or sell it for good money, bc the complete duovalve assembly is a little bit expensive. i paid around 280 Euros here in germany. The part Number is A000 830 38 84 You can also check for A1268300084. This is complete duovalve, too but for cars without heated windshiels, which are RHD-models. its also available but its more expensive. but doesnt make a difference if you only need the magnet lift. btw. i would not recommend changing the whole assembly (the plastic housing where the cooling hoses came in) because its a nightmare of work and this part usually doesnt break. hope this is a little bit helpful. greetings from germany and sorry for my bad english.
@@vornamenachname5589 Danke! Thank you for the very detailed research. On a trip to a local MB dealer they told me that the complete mono valve assembly is no longer available. With the part number you provided it may be worth to investigate if they can get that part as well here. Fortunately, there is no shortage of after market valves so getting replacement rubber parts is no problem as long as the original spring is still intact. Thanks again and good luck!
hi......i like all your handy tips.....i live in Aust,......i have a couple old w126..380,s.....a going car and one for spares.........car been sitting a long time but runs......no heat.......no fan belt on air con....probably seized anyway.......i took the mona valve out of my parts car, which still runs...and with operative heater......and put it in the daily driver...still no heat...fan working......there is a pump? at bottom of housing for thermo valve....could this be the problem...thank you
Nice to hear from you. Remove the power plug from the mono valve. It is fully open when de-energized. You should have heat at idle. Depending on what other issues you may have you either continue to have heat when you rev the engine to a higher speed. If the heat picks up and it gets warmer it could be the aux pump for the heater. It sits behind the removable portion of the firewall. If that is seized (and they do lock up with old age) it typically also takes out the CCU (Climate Control Unit). You will need to remove the firewall piece and remove the ABS control computer as well as it's holder screws. Smaller fingers are required to fish the little screws and nuts behind the wall and under the plastic wiper cover. You do not have to drain the coolant from the engine though to get the pump out. See if that motor works and the shaft spins easily. I put a 1Amp fuse into the circuit in order for the CCU to never blow because of the pump locking up. A locked up pump will not cause a total loss of heat though. It only means little to no heat at engine idle. Good luck.
My 560sel won't reach operating temperature in today's 0 degree Fahrenheit weather. It barely goes past 40c on the gauge. This sounds more like a thermostat problem. Do you agree? I'm hoping it's not the mono-valve. It looks like nos mono-valves are $300 on ebay.
Yup, that is usually the t'stat gone bad. As for the mono valve situation there is a relative cheap fix: assuming that you had a working original one, you really only need to change out the busted rubber diaphragm. Buy an aftermarket valve and just swap out that part. Here is the link: www.pelicanparts.com/More_Info/64118390132.htm?pn=64-11-8-390-132-M253&gclid=Cj0KCQiAwJWdBhCYARIsAJc4idDuK107FaN2Xhuy25hcvULXo7LOvOdnYc6jEONjcW6Bc-2i2ejSREAaAmhPEALw_wcB
@@straybenzes Thanks for the great suggestion. It's always something with these cars. After I get the thermostat replaced, I have to somehow magically get my glovebox door open that is jammed shut.
Thanks! Chain and guides were supposedly done by the previous owner. I seriously doubt that it had been done though. This may become another future topic for a video. Have a great rest of the week.
@@straybenzesThat would be phenomenal! There are no good quality videos on this subject on YT. I have 58K miles on my 420SEL, and those guides and chain are the elephant in the room, as I get distracted by all the other minor things. Have a great rest of your week as well.
That is exactly the problem: MB finally stopped making this part. If you have the original one and the diaphragm is torn you can buy a cheap after market valve insert and just replace the rubber part. The best of luck to you!
Good news! 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.
Hi Ralph.. I started getting. Cold air except for the defrost. Monov valve looks good. I unplugged it and checked the voltage on the pin. CC off 14.3v CC Defrost, High Fan, Max Temp 1.4v CC Economy, High Fan, Max Temp 13.9v Should it not be the same for defrost and economy. It seems that the economy is closing the monovalve?
You should have full heat with the valve unplugged from power. If that is not happening then I would say that the MV diaphragm may have a tear in it. Good luck.
@@charlestimmis273 Not necessarily. This phenomenon can also be caused by a malfunctioning cabin temp sensor blower motor. There is a video about troubleshooting the whole cabin temp system on this channel that I did a few years back. That should offer more pointers. CCUs do fail, but I have found that most of the time it is something a lot simpler and less expensive than that. Good luck.
When you pulled that out did all your coolant pour out the bottom? I took mine out to check if it was ripped and it was but I noticed all the coolant drain out the bottom of my car when I pulled the valve out. I also release the pressure from where the coolant pours in.
Hello.i got an mercedes benz a class a170,1.7 petrol,2005,before Christmas i was in holliday,before to i go my car in the morning works perfectly,even in the morning,at -4 ,-5 grade in couple of minutes was warm in the car...when i comeback from holliday my car heating work but poor,i can feel it very low,on first level on air conditioning..now heating still dont work,but car is no overheating,no noices,just heating dont work properly...i cant fell a little bit of warm air coming from dashboard hole but very low..what i can do?
This one is really difficult to assess from afar. It is either an electrical or a mechanical issue. Assuming that you changed your cabin air filter recently it could be the blend door actuator. The blend door actuator plays a role in controlling the temperature inside your car. If the blend door actuator fails to fully open the blend door towards the heater core, it will result in poor heating performance. The most common symptom of a faulty blend door actuator in Mercedes-Benz A-Class is a slight clicking sound (or other unusual noise) repeatedly coming from under the dashboard. The sound will be most prominent for a few seconds when you turn on the air conditioning or adjust the temperature. Here is more on that from this website: www.wheelsjoint.com/mercedes-benz-a-class-heater-not-working-causes-and-diagnosis/
Good news! 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.
Is the rubber part defective? If yes, get the cheap valve and replace the rubber part on your broken one with the one from the cheap one. I will need to do more research on what company can provide a properly working valve.
Good news! 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.
Ralph, my Mechanic came through like a champ. He found me a used one from a R107 being parted out and it works like a champ. The tube does not have a spring, it returns by vacuum, the problem is that MTC does not use the right metal for it to work when the electromagnet gets energized. I scavenged one of theirs and put their diaphragm on my original one and have it as a spare. Also kept the third MTC I bought for the diaphragm. Just in case, but that info on the BMW number is great news. Thanks
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In case you are driving in winter and need some heat in the car before you can make the repair, I discovered that if you just remove the electrical connection to the mono valve assembly you will get constant heat. This worked for me with my 86 560 SEL
You raise a good point. If the mono valve's rubber diaphragm is busted this method will not go into full heat mode. If it is the much more expensive problem for your climate control unit being busted, then pulling the plug on the mono valve will "restore" heat for the winter. It is very warm inside the cabin without opening a window thought. Good luck!
I keep an old car speaker Handy and use it to rub my screwdriver on to magnify it and BAM no lost screws!!! Awesome videos friend!!
Thanks for sharing your tip. All the best
Thanks for the video!!!
Thank you.
Awesome video, sir!
Thanks!
Unfortunately this part isn't available anymore. There are aftermarket parts, but they dont work. Thats sad, because i have a dualvalve and need two of them.
Btw. very good video.
There is a band aid fix: If you still have the OEM mono valves and only the rubber diaphragm is kaput then you can buy aftermarket ones and change out only that part. It really comes down to having a good seal whilst retaining the original springs. That is assuming the springs are still ok in the old valves. Good luck!
@@straybenzes Thank you for your advice. Unfortunately the aftermarket parts are also hard to get these days.
But after some research i found another way to get original parts. Even if the lift magnets arent available anymore, the whole Duovale is still in stock. This includes 2 lift magnets.
i know in US and maybe canada this cars were sold with automatic AC only, so they have monovalves. a MB dealer will tell you the whole duovalve assembly does not fit for your car with monovalve, adter checking your VIN. but of course you can take out the part with the magnetic lifts and the coil and install one of these in a car with monovalve and save the other as spare part or sell it for good money, bc the complete duovalve assembly is a little bit expensive. i paid around 280 Euros here in germany.
The part Number is A000 830 38 84
You can also check for A1268300084. This is complete duovalve, too but for cars without heated windshiels, which are RHD-models. its also available but its more expensive. but doesnt make a difference if you only need the magnet lift. btw. i would not recommend changing the whole assembly (the plastic housing where the cooling hoses came in) because its a nightmare of work and this part usually doesnt break.
hope this is a little bit helpful.
greetings from germany and sorry for my bad english.
@@vornamenachname5589 Danke! Thank you for the very detailed research. On a trip to a local MB dealer they told me that the complete mono valve assembly is no longer available. With the part number you provided it may be worth to investigate if they can get that part as well here. Fortunately, there is no shortage of after market valves so getting replacement rubber parts is no problem as long as the original spring is still intact. Thanks again and good luck!
hi......i like all your handy tips.....i live in Aust,......i have a couple old w126..380,s.....a going car and one for spares.........car been sitting a long time but runs......no heat.......no fan belt on air con....probably seized anyway.......i took the mona valve out of my parts car, which still runs...and with operative heater......and put it in the daily driver...still no heat...fan working......there is a pump? at bottom of housing for thermo valve....could this be the problem...thank you
Nice to hear from you. Remove the power plug from the mono valve. It is fully open when de-energized. You should have heat at idle. Depending on what other issues you may have you either continue to have heat when you rev the engine to a higher speed. If the heat picks up and it gets warmer it could be the aux pump for the heater. It sits behind the removable portion of the firewall. If that is seized (and they do lock up with old age) it typically also takes out the CCU (Climate Control Unit). You will need to remove the firewall piece and remove the ABS control computer as well as it's holder screws. Smaller fingers are required to fish the little screws and nuts behind the wall and under the plastic wiper cover. You do not have to drain the coolant from the engine though to get the pump out. See if that motor works and the shaft spins easily. I put a 1Amp fuse into the circuit in order for the CCU to never blow because of the pump locking up. A locked up pump will not cause a total loss of heat though. It only means little to no heat at engine idle. Good luck.
My 560sel won't reach operating temperature in today's 0 degree Fahrenheit weather. It barely goes past 40c on the gauge. This sounds more like a thermostat problem. Do you agree? I'm hoping it's not the mono-valve. It looks like nos mono-valves are $300 on ebay.
Yup, that is usually the t'stat gone bad. As for the mono valve situation there is a relative cheap fix: assuming that you had a working original one, you really only need to change out the busted rubber diaphragm. Buy an aftermarket valve and just swap out that part. Here is the link: www.pelicanparts.com/More_Info/64118390132.htm?pn=64-11-8-390-132-M253&gclid=Cj0KCQiAwJWdBhCYARIsAJc4idDuK107FaN2Xhuy25hcvULXo7LOvOdnYc6jEONjcW6Bc-2i2ejSREAaAmhPEALw_wcB
@@straybenzes
Thanks for the great suggestion. It's always something with these cars. After I get the thermostat replaced, I have to somehow magically get my glovebox door open that is jammed shut.
@@Cpcsof1 Yup. There is indeed always something to work on. They are over 30 years old and one can expect for stuff to go sideways. Good luck.
Thank you for the great video! Have you had to replace the timing chain/guides on your 420 SEL?
Thanks! Chain and guides were supposedly done by the previous owner. I seriously doubt that it had been done though. This may become another future topic for a video. Have a great rest of the week.
@@straybenzesThat would be phenomenal! There are no good quality videos on this subject on YT. I have 58K miles on my 420SEL, and those guides and chain are the elephant in the room, as I get distracted by all the other minor things. Have a great rest of your week as well.
Great video!!! Very informative. Where do you recommend anyone can purchase this part.
That is exactly the problem: MB finally stopped making this part. If you have the original one and the diaphragm is torn you can buy a cheap after market valve insert and just replace the rubber part. The best of luck to you!
@@straybenzes where can you buy the cheap after market valve insert to replace the rubber part?
Good news! 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.
Hi Ralph.. I started getting. Cold air except for the defrost. Monov valve looks good. I unplugged it and checked the voltage on the pin.
CC off 14.3v
CC Defrost, High Fan, Max Temp 1.4v
CC Economy, High Fan, Max Temp 13.9v
Should it not be the same for defrost and economy. It seems that the economy is closing the monovalve?
You should have full heat with the valve unplugged from power. If that is not happening then I would say that the MV diaphragm may have a tear in it. Good luck.
@@straybenzes I do have full heat with it unplugged. does that mean Cliamte control unit is shot?
@@charlestimmis273 Not necessarily. This phenomenon can also be caused by a malfunctioning cabin temp sensor blower motor. There is a video about troubleshooting the whole cabin temp system on this channel that I did a few years back. That should offer more pointers. CCUs do fail, but I have found that most of the time it is something a lot simpler and less expensive than that. Good luck.
When you pulled that out did all your coolant pour out the bottom? I took mine out to check if it was ripped and it was but I noticed all the coolant drain out the bottom of my car when I pulled the valve out. I also release the pressure from where the coolant pours in.
That is strange. There is a slight coolant loss, but really not much as this spot sits much higher than the engine, radiator, and heater core.
Hello.i got an mercedes benz a class a170,1.7 petrol,2005,before Christmas i was in holliday,before to i go my car in the morning works perfectly,even in the morning,at -4 ,-5 grade in couple of minutes was warm in the car...when i comeback from holliday my car heating work but poor,i can feel it very low,on first level on air conditioning..now heating still dont work,but car is no overheating,no noices,just heating dont work properly...i cant fell a little bit of warm air coming from dashboard hole but very low..what i can do?
This one is really difficult to assess from afar. It is either an electrical or a mechanical issue. Assuming that you changed your cabin air filter recently it could be the blend door actuator.
The blend door actuator plays a role in controlling the temperature inside your car. If the blend door actuator fails to fully open the blend door towards the heater core, it will result in poor heating performance. The most common symptom of a faulty blend door actuator in Mercedes-Benz A-Class is a slight clicking sound (or other unusual noise) repeatedly coming from under the dashboard. The sound will be most prominent for a few seconds when you turn on the air conditioning or adjust the temperature.
Here is more on that from this website: www.wheelsjoint.com/mercedes-benz-a-class-heater-not-working-causes-and-diagnosis/
Tell us what engine you have on your 126 and what year.
Is the monovalve same for all engines and years..thank you
Hi there. The mono valve is the same on all US spec W126. This was a 420SEL.
@@straybenzes thank you
Good news! 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.
Ralph, I got a big problem...I cannot find a Mb monovalve anywhere... all I can get are the MTC ones and they are garbage. What do you suggest I do?
Is the rubber part defective? If yes, get the cheap valve and replace the rubber part on your broken one with the one from the cheap one. I will need to do more research on what company can provide a properly working valve.
Good news! 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.
Ralph, my Mechanic came through like a champ. He found me a used one from a R107 being parted out and it works like a champ. The tube does not have a spring, it returns by vacuum, the problem is that MTC does not use the right metal for it to work when the electromagnet gets energized. I scavenged one of theirs and put their diaphragm on my original one and have it as a spare. Also kept the third MTC I bought for the diaphragm. Just in case, but that info on the BMW number is great news. Thanks
@@SailingRegulus Great job!
300..?
300? I am not sure what your question is.