My 1990 300CE puts out both cold and hot air at the same time. The hot air comes from the left and right side vents and on the left side of the center vent. Cold air comes out of the center vent in the middle. What could be causing this?

Someone told me that the board behind the AC controls is at fault.
If so, can reconditioned boards be bought?

Any help on this subject would be greatly appreciated!

go.dale@verizon.net

More likely, the blendor motors have failed. In my case, I disconnected the battery and reset my computer and it took care of it, but this is the exception...usually, a very expensive fix.

It could be anything from the duovalve unit malfunctioning to a bad a/c pushbutton assy. Have seen both of these components fail and cause this problem . You would have to get a electrical diagram and stsrt troubleshooting.

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euro 287
Mercedes Technician 7 Years (retired to Hyundai)
2000 Dodge Durango
98 Mazda truck

I think that 99% of Mercedes climate controls experience warmer air from the side (dash) vents with age. I believe it is a vacuum leak, or some sort of air leak.
If you do a search, you'll find information on this problem; it's been discussed several times.
Good luck!

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2006 E350 w/ 155k miles (Daily Driver)

Previous:
1993 300E 3.2L Sedan w/ close to about 300k miles
2003 E500 Brilliant Silver (Had 217k miles when totalled!)
1989 300E with 289,000 miles (had for <1 yr while in HI)
03 CLK 500 cabrio (Mom's)
2006 C230k (Dad's)
1999 S420 (Mom's/Dad's)
2000 C230k Sport sedans
2001 CLK320 Cabrio (Mom's)
1995 C280 My First Mercedes-Benz... (155k miles. EXCEPTIONAL AUTOMOBILE. Was Very hard to let go of!)