I've got the same problem with my CCU. Can someone please point out which exact joints need to be re-soldered on the board? Or is it as simple as cleaning a relay? If so, could you point out what exactly needs to be cleaned in the picture you attached?

I've taken the solder gun to my CCU numerous times without any change in functionality.

Thanks.

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1984 300 SD 384,000 Miles

ProgRama is in your future:

ProgRama 123 830 12 85 Mercedes Benz Climate Control Unit


You do know the definition of insanity..........??

The contacts in the relays will be readily apparent when viewed "in person." The relays themselves are the items with the copper wire coils.

I am unwilling to send it to Programa because I bought this unit new about 5 years ago. They are obviously poorly manufactured and I would like to know the workings of how to fix it next time something happens with the unit.

tangofox, I've seen the copper relays. Do you know which one activates the specific function? As far as cleaning, are you saying to just taking some rubbing alcohol to the coil with a q-tip? So this failure has nothing to do with soldering?

Thanks.

__________________
1984 300 SD 384,000 Miles

Cleaning the contacts ususally involves removing oxidation. That typically requires sliding some fine abrasive paper between the contacts while they are held closed. And there is aerosol "contact cleaner" available.

The schematics identify the function of the various relays, but I don't believe that the actual relays are so labeled. I would submit that it is easier to clean them all than it is to identify specific function of each. Generally, the relays operate the various vent flap valves and the blower fan.

Yep, would not send it to ProgRama either my unit crapped out after 14 months. They do not honor 3-year warranty, want you to send unit to supplier even though supplier only have 1-year warranty.