resoldering ACC panel
 

A friend with '85 300TD has an erratically functioning climate control. Based on the help here, I diagnosed it as a bad control panel and we pulled it out. Many of the solder joints look poor. He is afraid that some of this was intentional and that fully soldering all connections may prove harmful. I don't believe that to be the case--why would anyone insert a wire, or component thru a hole in a circut board and not want it soldered?
So whats the deal? Do we just solder all apparent connections?

Yes, but make sure you don't bridge any traces, only heat the joints and add a little solder. Don't use an iron that is too big. A 25 or 40 Watt iron will do fine. Using an iron that is too big can lift circuit board traces.

There were some circuit boards that were soldered poorly. Making good solder joints may very well cure your problems in the case you describe.

Good luck,

I had a similar situation and what I found was the relays on the circuit board, I think there was about 5 of them, had corroded contacts. I took a meter and checked the continuity on the relay contacts and found most of them had no contact or a poor contact. I cleaned them up with a piece of fine sand paper and it is still working fine, that was about 2 years ago.

This was on a 1981 300SD.

Phil

I have flakey problems with the ccu also. I can get the bottom panel off to view the circuit board, but can't seem to get at the top without destroying the unit. How is it done?

Wow, your asking me to remember something I did 2 years ago... I do remember having a problem opening the top side of the unit. There was something with the switches on the front panel. I remember I almost destroyed one of the switches before I figured out how it came apart. I think there was some kind of a bar that slid sideways where the switches come through the metal box....??? I think it locked the switches in position. Hope this helps.

If you could post a picture of the front of the unit it might help.

Phil