Heater probs

[Ian B Walker]

This is embarrasing but I need some advice as I do not know what, or how to do something. This post could be classed as electrical too so I am awaiting my knuckles wrapped

OK the problem, I cant turn off the heater in my 124 coupe. Duo valves have power although I am not sure is they should have. I am totally useless when it comes to my cars and electrics, I suspect this is an electrical problem. I am off to South of France in a month, temp there right now is 33c. Last thing I need is a heater on full blast.

 

[shandy]

Ian,
The default setting on the duovalves is full flow,that is, when there is no power you will have full heat. When the heater is turned on you should hear the valves clicking as they open and close, the frequency depends on where the temp.control is set.
Are both sides of your heater stuck on ?
Geo.

 

[Ian B Walker]

Are both sides of your heater stuck on ?
Geo.

yes they are.

 

[grober]

Nightmare!

I take it you dont have aircon Ian?? Nightmare to trouble shoot! One possibility If your temperature sensors have gone open circuit or are disconnected. One is easy to get at -its located in the front interior light courtesy housing. If you remove the cover you should see it. It will have electrical connections to it and a small tube for ventilation of the sensor On cars with sunroofs this is even fed by a small blower motor. The other heater matrix sensors are located behind the dash control unit. If any of them is disconnected or open circuit then the system may "think" the car interior is cold and try to heat up the interior overiding the manual temperature controls. Some of the air distribution flaps may be pneumatically activated so it pays to check their vacuum supplies also. I think theres a seven way vacuum distribution manifold behind the glove box to all the actuators. I read a post somewhere about checking their vacuum integrity individually at the manifold with a mityvac tester to see if they are working/leaking before taking the heater to bits. These are just educated guesses and in this case you need to talk to someone who knows these systems inside out or has been brave/foolish enough to take one to bits!! Most people do this if the fan motors fail and there are numerous posts about this which may contain the info you need. Good luck!

 

[KillerHERTZ]

I know how you feel Ian, I had no heat during the whole winter, now its stuck on full

 

[DieselE]

This is embarrasing but I need some advice as I do not know what, or how to do something. This post could be classed as electrical too so I am awaiting my knuckles wrapped

OK the problem, I cant turn off the heater in my 124 coupe. Duo valves have power although I am not sure is they should have. I am totally useless when it comes to my cars and electrics, I suspect this is an electrical problem. I am off to South of France in a month, temp there right now is 33c. Last thing I need is a heater on full blast.

Given your latest business venture, there is a touch of "Physician heal thyself" about this thread.

 

[Ian B Walker]

Given your latest business venture, there is a touch of "Physician heal thyself" about this thread.

Yes I know, embarassing to say the least. But I am honest, I didnt and still dont know whats wrong (wife took car this morning ) I have learnt many things in life, one of them is if you dont know, ask. No better place than this to ask is there? When I have learnt I will pass on what I have learnt. :bannana:

 

[grober]

Remember this page IAN. MIGHT COME IN USEFUL??? http://photos.orange.co.uk/album/1259925
some more pics here http://www.w124performance.com/images/W124_dash/
and a post about pneumatics on the heater/aircon unit
http://www.mercedesshop.com/shopforum/showthread.php?t=35373&highlight=heater+controls

 

[grober]

Worst comes to the worst you could just bypass the system for your sojourn to France. No heater but no heat either!

 

[MangoMan]

I know I'm most probably going to get shot; but have you checked your fuse?

Running & Ducking @ the same time................

 

[Ian B Walker]

Ok as promised I have located the problem. I have removed the roof light and cleaned out the sensor housing. Made no difference. Stripped out the center dash and removed the dual wheels unit, cleaned and re fitted. No difference. Stripped down the duo valve and cleaned out, checked for continuity. Partial success. Checked out the flow motor on the duo valve, no power because the two cylindrical parts of the valve are intermitant. Checked with a duovalve from a 124 estate and it functions. However I need the item with the feed motor. So Been in touch with a breaker and he is sending me one which I will get tomorrow for the princley sum of £60. New one, sit down........................ £238 inc VaT

 

[grober]

Result!

Result! Not the dreaded pneumatics after all and thankfully no taking the dashboard completely to bits.Hope the breaker one turns out OK.

 

[Motard]

Really good that you get some practice in Ian then you can do the same with mine when you come down here

 

[Ian B Walker]

Final Update

Got a replacement duo valve and fitted it. Mmmmmmmm cool air once more. No burnt feet etc. Now watch the weather change to cold