phb2phb3

I have a 2007 S550 4matic with rear dual zone climate control. A few months ago I noticed the rear vents were only blowing very hot air despite setting the controls to any temperature, even the coldest setting. This issue remained whether on auto or manual control. When I shut the rear climate control off then the center console becomes extremely hot. I reviewed several posts that described similar issues and all recommended replacing the "heater control valve (solenoid valve)". This is the part that is located on the firewall just under the wipers on the driver side in the engine compartment. I ordered the part from Pelican Parts and replaced it with some difficulty as the C clamps are difficult to reach in this tight space. After about 2 hours of "fun" I finally completed the replacement only to find the problem with the rear heater was still there, no improvement. I would appreciate any thoughts or suggestions regarding this issue and I would seriously like to avoid taking the car into the dealership for a diagnostic.

Also of note: the right side blows very hot, the left side blows warm. Front climate control works perfectly but when rear is turned OFF then hot air bleeds through center console and cup holder area.

WilliamMB

Hi all, I have 2007 S550 with the exact same issue. I replaced the heat exchange control valve located under windshield wipers and same issue still. Any idea of what could it be? I scanned the A/C and I got two codes, 920A ( A31/1m1 circulation pump overload) and 9375 (A31/1y2 RIGHT DUO VALVE SHORT CIRCUIT TO POSITIVE OR OPEN CIRCUIT)

robohopar

hmm interesting..now that I think about it my rear passengers were complaining that the door sill vents were not blowing cold air...

gluck guys, I think i need to sell my car :/

nishboo

Did you find a solution?

evansw220

For the rear a/c units there's a duo valve located behind the passenger front fender liner..

Jackieboggs1956

Correct, had same problem on 2008 S550, let it go to long, cracks developed in the wood/plastic from the heated console. Under the front right fender is where the valve is located. Fixed my problem

Nickthegreek

Yup sounds like it's the duo valve/heater control valve. It sits in the front passenger side fender. It's not cheap it's about 400 for the part. I'll get a part number on it for you if you want

just1time

Please do. Mine has been like that for a year. Luckily no one is ever in my backseat.

CarPartsDiscount.com

hey guys, i would need to know the factory part # to be 100% sure but these are the valves that i offer, i hope this helps. if someone can provide the factory Mercedes number i can cross reference to be positive.

https://www.carpartsdiscount.com/cat...html?3594=2215

Please let me know if i can be of any further assistance

mgokool

Just fixed mine...see my post here, hope it helps you guys fix your issue.

https://mbworld.org/forums/s-class-w...-hot-cold.html