starting this year my wife turn on the a/c and only hot outside air blowes out on the driver side. passenger side is fine...does anybody know which valve has quite working and give me a general idea of where to fine it? iam sure that the dual climate control isnt turning off outside air valve and i dont know where to start...I have switch the controls back and forth without any change except the heater on makes it hotter

Most likely several ounces low on refrigerant.

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Select "LO" on both temperature settings and disengage the compressor with the "EC" button. After the system stabilizes, you should have the same (warm) temperature air out of both sides. If you do, the problem is in the cryogenic system. If the driver's side is still warmer, the problem is in the heater system.

The cryogenic problem is most likely that you are low on refrigerant, as MB Doc indicates.

that;s not the problem, i have the same problem on my 99 e300, look for a dual valve that controls the temp for both of the heater cores, its located by the cpu on the passenger side close to the strut. they get stuck just tap it a few times and if that works then u should be able to take it apart an clean it. good luck....

Don't be so sure. This is a common complaint on the W210 and is rarely the duovalve. If you have warm air out of the right side, however, it is almost certainly the duovalve at fault.

The way to tell is to turn off the compressor and check temperatures. Just like I said above.

Same problem on my W210 was caused by low charge - this is VERY common on the W210 and the duovalve issue is not as prevalent. The best thing is that it's a CHEAP fix!

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08 W251 R350
97 W210 E320
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86 W126 560SEL
85 W126 380SE Silver
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thanks, i will check tonight .... my wife thanks u in advance if it works

thanks for the advice....everyone was correct the A/C was a little low ..got gages out topped off and momma is "Happy Camper" again

I have a similar problem but my AC blows nice and cold for 5+ minutes and then just seems to shut off. This happens on both sides. The air keeps blowing but it just turns the outside temp. If I stop and sit at idle for a few minutes it will get cool (not cold) again.

Last year I was told to clean the duovalve which I did. It was a little sticky and it was fine after the cleaning. Some one mentioned another valve under the steering wheel. Any one know what that is called?

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Andy, North Jersey
1999 E300 TurboDiesel 116k miles

Check for codes and read the current-sensor values. There are a lot of things that could cause this kind of behavior.

I'm not sure what valve would be under the steering wheel. The evaporator temperature sensor is near there, as is the expansion valve (but you get to that from under the hood).