I've got the driver's side air warmer than the passenger side problem. Tried to clean up the duovalve yesterday as suggested in this thread - http://www.benzworld.org/forums/forums/thread-view.asp?tid=1178385&posts=14&fid=17.
No change - still warmer on the driver's side. After I was finished, I wondered if I had disassembled the duovalve far enough. I did not drain the coolant and had no coolant loss. In fact I ddin't even see any coolant. All I did was take off the two covers, pull up the electrical cover and clean up and lube the two pistons I saw. I did not remove the plate separating the top of the unit from the coolant. Should I have done so and is there more to clean and lube under that plate?
The warm driver's side air problem can have other causes. It is often due to low R134a A/C refrigerant charge. Basically, the passenger side of the A/C evaporator is cooled first. If you're low on refrigerant, there won't be enough cold refrigerant left to cool the driver's side.
Have you run the A/C diagnostics yet to get the sensor readings? The sensor readings will tell you whether it's a duovalve problem or A/C charge problem.
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