W210 blower changes speed by itself

[mykaitch]

I don't have climate control, just air-con. Sometimes I turn the blower switch off and the fan still runs, other times it changes speed itself. If I play with the control switch it clears the problem. Changed blower reg six months ago (new part from MB) and it seemed to be okay. MB gave me another today to try in case it has gone again. Anybody heard of this ???
(No, not MB GIVING a part...)

Thanks

 

[Diesel Benz]

I did not check if the fan regulator is the same with the automatic AC but on my W210 the regulator failed with the same symptoms as you describe. I've seen this happening on several W210 cars but one guy had it also on the W211.

 

[mykaitch]

Thanks, if it has happened before and been fixed with a regulator I will fit the one my dealer gave me and try again - I say gave, what I mean is lent really to see if the one I bought six months ago has failed. Just hoping it's not the A/C ECU.

 

[mykaitch]

Fitted the new part -you don't have to take the motor out so it's easy. First thing I noticed is that the very low speeds like the one marked with a fan work - I am sure it did not on the last 'new' part...Time will tell. As an electronics boff, the regulator is potted ie after the pcb is assembled it is placed inside the cavity and filled with a resin or potting compound. I have had several problems in the past whereby the setting of the resin (which usually involves heat) stresses the pcb and in particular, can damage solder joints. Just a thought. Checked every number on new and last new part and they are the same.

 

[Diesel Benz]

What was the part number, was it A2108700210 (this one has replaced the older part A2108206210)? The one for RHD auto AC should I believe be A2108201017.