1998 C230, 125,000 miles.

On more than one occasion, but very sporadically, I've had the AC on and good cold air coming through all vents except the left/drivers side dash outlet. This vent has really, really HOT, super hot air coming through it. I'm in Phoenix, AZ. OAT was about 100F (at Midnight!!).

Historically, the problem would disappear upon start up the next day, and only return out of the blue with no apparent reason. It has happened three to four times since I purchased the car in Nov. 09. Had a full freon charge a few months ago and with a few little quirks, the AC works very well and is super cold.

What do you think? Thank you.

the heater valve is dual zone[left and right]the left side is failing.replace heater valve[i'm assuming that freon charge is correct by what you stated because on those cars low charge will give cold on one side and not on the other]

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David S Poole
European Performance
Dallas, TX
4696880422

"Fortune favors the prepared mind"
1987 Mercedes Benz 420SEL
1988 Mercedes Benz 300TE (With new evaporator)
2000 Mercedes Benz C280
http://www.w108.org/gallery/albums/A...1159.thumb.jpg

Do you have manual or auto controls? If I'm not mistaken the manual controls have dual zone operation and the auto is single zone.

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1989 300CE

The car has the automatic 'set it/forget' controls.

You should read the values of the temperature sensors in the system through the diagnostic function of the pushbutton unit. Go to this link and read about it.

http://www.startekinfo.com/manual/volumes/cc/3_7/m12.jsp

Check the heater temp (#3) and evaporator temp (#5) and report back.

There is also a possibility that the refrigerant charge is low. But do the above test first and tell us what you get.

Very interesting, thank you- I'll try it out.