w211 climate control fault.

[Swampy_B]

I have a problem with my a/c (4 zone thermotronic), front vents lovely and cold but the back blow hot.

Had this fault diagnosed by MB Stealer who said:

Heater control unit (a2118300285) & motors x2 (a2038201642) needed replacing.

I took it for a second opinion and showed them the quote (more like a part number though) from stealers who had the car for 2 days to strip it down and located fault.

Independent Merc Diag advised only 1 of these parts would break not all 3 together. when he ran autologic it reported a heater exchange fault and he was certain that was the cause.

I'm total confused and todays hot weather has annoyed any back seat passengers and me.

Please can you help me.

Should all 3 go at once?, could the exchanger be the prob?, have you had a similar fault?.

Ta

 

[mr. shr]

My Dad's W211 did exactly this.
I don't know what the fault was but I think it's quite common.
Could it be a duo valve problem?

I'm sure others here will soon be able to provide some solutions.

 

[lingsim]

Sorry, cant really help, but had the exact same fault, was fixed under warrenty free of charge, so i didnt really ask any question!

 

[mr. shr]

Sorry, cant really help, but had the exact same fault, was fixed under warrenty free of charge, so i didnt really ask any question!

Yes, my Dad's was also done under warranty so don't know the details.

Must be someone on here that can help with this?