Heater not working properly..please help

[blackc230]

Please Help!!

The heater in my C230 is not working properly. It only either blows HOT air or COLD air only. I cannot get it to blow medium temperature air through the vents.

My workshop checked everything including the water pump and it seems to be working fine. The only doubt that I have is with the dual valve. Okay...here's the scenario. If I scroll the temperature regulator to about half way b/w HOT and COLD, the air coming out of the vents is COLD (all 4 vents). But when I scroll it all the way up to HOT..the air becomes HOT. And this only happens to the 2 driver side vents. The passenger side does not blow hot air at all.

Is this how temperature regulator in all W202s should work? Do I need a new dual valve thingy?

Does anyone have some sorta diagram showing all the heater process in W202s?

thanks in advance

[69chevelle]

I have the same car with the dual climate control and I've been experiencing this problem also.. I gotten so fed up with it that I just leave the heat on high at night and cold in the daytime. The air conditioning works fine.
Does your EC red led light flicker on and off sometimes?

[blackc230]

Originally posted by 69chevelle
I have the same car with the dual climate control and I've been experiencing this problem also.. I gotten so fed up with it that I just leave the heat on high at night and cold in the daytime. The air conditioning works fine.
Does your EC red led light flicker on and off sometimes?

Nope..the EC stays off and my air con also works fine.

How does the heater system work anyway?

[blackc230]

just got back from my workshop and according to them the motor that opens and closes the flap (the flap that regulates the amount of heated air blown into the cabin) is not working.
Now I'm in real difficulty finding the parts. Since the car has not been taken apart, noone knows for sure whats not working.

Can anyone here help me out? To me, the flap motor explanation thing makes sense...PLEASE HELP...

I know this may sound ridiculous making a big deal outa this heater thing for some of you. But I just wanna make my car in full working condition.

thanks guys

[xvvvz]

I don't believe it is a motorized thing. I believe it is a vacuum operated device. The vacuum system is a common problem as the cars get older and the vacuum system develops leaks in the hoses, connectors, manifolds, etc.

Visit this thread:

http://www.club202.com/forums/showthread.php?s=&threadid=12406&highlight=vacuum

[xvvvz]

Did the duo valve check out OK?

[blackc230]

Originally posted by xvvvz
Did the duo valve check out OK?

I think the valve checked out OK. There's a click sound when the air con is switched on and there's radiator water coming out of the hose.

They did mention about the hydrolic system that controls the flap. Is it an easy thing to fix? is it possible to get the part #? My car is C230 1997

thanks

[OzC36]

Take a look at the Heating Ventilation system parts for your car:

http://www.detali.ru/cat/oem_mb1.asp?TP=1&F=202023&M=111%2E974&GA=722%2E600&GM=717%2E417&CT=F&Cat=44V&SID=83

The problem part is probably in here:

http://www.detali.ru/cat/oem_mb2.asp?TP=1&F=202023&M=111%2E974&GA=722%2E600&GM=717%2E417&CT=F&cat=44V&SID=83&SGR=045&SGN=01

You might need to get an electronic diagnostic check from a Mercedes independent mechanic to isolate the AC system fault.

[kevinzorz]

I have a related problem, my middle vents do not blow, but the vents right under the windshields do. How do I turn the ones by the windshield off, and turn the middle ones on?

[blackc230]

Thanks for your replies.

Well, I went to another workshop yesterday just to get a second opinion. This time, they have this computer device that plugs in to the car computer straight away and it tells you which electrical parts arent in good working order. At first they thought the control unit is broken. But when tested, the control unit seemed to be working as it should be. When adjusted, the temperature went up and down on the screen. But the temperature on the duo valve didnt change. They reckon the duo valve needs replacing.

any opinion on this matter?

thanks again

[OzC36]

xvvvz, thanks for the link on the dash removal.
Downloaded and saved for a rainy day!