Fixed the ACC!

[Jeremy5848]

Regular readers of this feature (that's you) will recall that Our Hero (that's me) had figured out (duh!) that the ACC in his favorite (and only) Benz was not being all that it could be. Specifically, with the air conditioning on, the blower would run "high" or "low" but nothing in between -- all the "Automatic" setting did was to run the fan at low speed. In Economy mode, all of the blower speeds would work correctly. In Defrost, it ran full speed as it's supposed to.

Since this was not a major problem, it was rather low on the priority list and I got to it only yesterday. Having read all of the information on climate control that had been posted here by you good people (bless you!), I strongly suspected that the push-button control unit was to blame. Yesterday I removed it and discovered that several traces on the pc board were fried and some PO had done a rather poor job of repairing them. A picture of this disaster was posted here:

Fried ACC Board (picture) due to frozen aux pump?

Since the fried traces may have been caused by a frozen auxiliary water pump, I figured I'd better check it out before I fried something else. This adventure will be posted with pictures as soon as I finish the current tale. Suffice it to say that I checked the pump. It works, so I added a fuse, as recommended in several posts here (thanks!).

There isn't a lot to say about removing and replacing the ACC. Everything went pretty much as described by the many who have given step-by-step removal instructions. I thought it was interesting that the wood panel over the ACC was held on by clips so it could be easily popped off. The ACC was a tight fit coming out of and especially going back into its hole; there are a lot of wires and hoses to get in the way. It was clear that whoever built the ACC for Mercedes planned on the thing being serviced; it was easy to take apart and that was nice.

Today I redid the PO's messy jumpers and also resoldered all of the connections on the pc board, including the junctions to the little boards that hold the connectors. There are now a total of four jumpers on the board, replacing four fried traces. These are shown in the two attached photos.

An hour ago, I put the completed unit back together and into the car, fired it up, and...it worked! I was so relieved! It's so frustrating to do a job like this (resoldering a pc board) when you're not sure whether there really is a problem and whether your hard work will do any good. This time it worked. May my good luck be contagious.

Happy Fourth of July. Let the fireworks begin.

Jeremy

Good job. Whenever I try stuff like this it usually fails.

[ImBroke]

Congrats!!!