W124 Heater always hot

[mtgraphics]

I have a 1991 230ce that has had a problem with regulating the heater temperature for the last few years, the current status is just red hot all the time, regardless of where the temperature wheels are positioned.
I have replaced the sampler motor, so it is drawing through the cabin air, and I have just rebuilt the duo valves and they are working fine when tested, my car does not have a/c, climate control etc, just left and right hand side temperature control wheels.
Any ideas out there as to what the problem could be to just let red hot air in the car all the time?

 

[wrdcc01]

The duo valve is not being controlled correctly. If you put the temp to full cold on both sides, are you getting a voltage on the duo valve? The controller is probably faulty if you are and if not then the valve is sticking.

 

[Smiley]

iirc the cabin temperature sensor is in the panel in the roof next to the sunroof switch. It can get clogged up with dust and that makes it think that the car is cold - very easy to take it apart and make sure it is clean in there.

 

[optimusprime]

Smiley Yes lots of owners dont even know its up there by the interior light switches ..small slotted vent.

 

[mtgraphics]

The duo valve is not being controlled correctly. If you put the temp to full cold on both sides, are you getting a voltage on the duo valve? The controller is probably faulty if you are and if not then the valve is sticking.

I've done a little testing and there is voltage when mid temperature and max cold, and no voltage when turned to max hot. I can also hear the valves click when the temperature is changed, so everything there is working fine.
I've taken out the cabin sensor and it is getting power and wasn't dirty but I guess it isn't working.
I'll have to source a replacement to see if solves the issue as I am now stumped!

 

[Smiley]

Make sure that the area in the roof space behind the sensor is not clogged up with fluff and dirt before you replace the sensor.

 

[mtgraphics]

Make sure that the area in the roof space behind the sensor is not clogged up with fluff and dirt before you replace the sensor.

Yes I've given it all, a good clean, just need to find a new part now, I'll give Mercedes a call for a price on Monday

 

[mtgraphics]

I still have this problem and really want to get it sorted, I've been reading a lot about this sort of problem being caused by vacuum pods, but all those threads have been about cars with A/C.
My question is, do cars without A/C still have all these pods controlling everything?

 

[grober]

I still have this problem and really want to get it sorted, I've been reading a lot about this sort of problem being caused by vacuum pods, but all those threads have been about cars with A/C.
My question is, do cars without A/C still have all these pods controlling everything?

YES -THESE VACUUM ACTUATORS OPERATE THE FLAPS THAT ROUTE THE AIR THRO THE HEATER AND HOW ITS DISTRIBUTED- THEY CAN FAIL OR THE VAC PIPEWORK CAN LEAK- LOTS OF STUFF ON LINE IF YOU SEARCH

 

[optimusprime]

Some pods easy to get to others are not . I would first check vacuum .If there is no vacuum then the flap on the pods wont open up

 

[optimusprime]

You need this free manual .. Google - Model 124 Maintenance Manual Index i dont think your engine will be in the manual but the heater section is all the same . for now click on M103 then go to item number 83 -568 .

 

[mtgraphics]

Thanks for the replies, I have spoken to a MB dealer today with my vin number and they have confirmed that my non a/c car does not have vacuum pods, just the duo valve system, and that is more than likely the route of the problem. Available from stock at £260.00, I think it's my only option as I've covered everything else.

 

[optimusprime]

Tell the mb dealers they can all go out and sell sand to the shiek of Arabia . All W124 have vacuum operated pods on the flaps of the heater box ,,they are operated by the movement of the heater controls .They dont want the job its a barsteward of a job to pull the dash out . But some pods can be worked on with out dash removal . But it was found that your problem is the duo-valves . So did you pull off the duo plug to make it run in default mode ??/

 

[grober]

Non Working Heater in 230E (again again again etc)

Got a J reg W124 230E. (non aircon) The heater doesn't work very often, and then it's only for a few minutes. I've checked the duovalve, and someone's already been in there and removed the valve stems, so water can flow through it freely. Also the electric heater pump is working. I've put a...

forums.mercedesclub.org.uk

Index of /images/W124_dash

e.g.

 

[mtgraphics]

Tell the mb dealers they can all go out and sell sand to the shiek of Arabia . All W124 have vacuum operated pods on the flaps of the heater box ,,they are operated by the movement of the heater controls .They dont want the job its a barsteward of a job to pull the dash out . But some pods can be worked on with out dash removal . But it was found that your problem is the duo-valves . So did you pull off the duo plug to make it run in default mode ??/

Yeah I've watched a video on the dash removal and the replacing the pods (but on a car with a/c), it's a lot of work. So are you saying the dealer is wrong with my car spec and there are pods?
Could you tell me about the duo valve default mode so I could try it?

 

[wrdcc01]

I've done a little testing and there is voltage when mid temperature and max cold, and no voltage when turned to max hot. I can also hear the valves click when the temperature is changed, so everything there is working fine.
I've taken out the cabin sensor and it is getting power and wasn't dirty but I guess it isn't working.
I'll have to source a replacement to see if solves the issue as I am now stumped!

Try opening it up and give it a clean or get hold of a rebuild kit if you can or a good used valve, This is a really simple device that just gets gunked up and sticks. It may click but if it doesn't stop the hot water flow then it's buggered. Very easy quick job to do but you need small hands to easily remove the thing, got any kids? You can do a top clean and check with it in situ though. Easy test and default if you like is with the valve electrical connector unplugged there should be no heat, the valves should be closed under spring pressure.
Watch this....

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[optimusprime]

The duo valve will always fail in hot mode .If you strip it down in the car use a magnetic screw driver ,,,the mall parts can fall out and you wont get them back . But pull the plug first to see if you can hear it open and close .

 

[Yorkee]

My 1994 E320 Cabrio had the same issue, blown fuse so fails to hot only.

 

[optimusprime]

Did you car have AC ?

 

[mtgraphics]

Did you car have AC ?

No air con, no vacuum pods.