I was actually speaking of cleaning the contacts within the ETR switch, which is what controls the evaporator temperatures.
If you are planning on trying to repair your pushbutton assembly, it can be disassembled and the contacts can be cleaned using electrical contact cleaner. I have used brake cleaner in a pinch, as it also leaves no residue. TV tuner cleaner leaves some lubricity for moving parts that donít carry current. Do NOT use carburetor cleaner, it will attack the plastics.
There are four little double pole relays on the circuit board Ė try cleaning the contacts by sliding some plain paper soaked with a bit of contact cleaner between the contact points. The other parts to clean are the sliding contacts for the buttons themselves.
I wonít start up another debate about the re-soldering of all the joints on the circuit board. IF there is a cold joint or one that has detached, this may solve some problems. Or, conversely, you could toast the components on the board depending on your finesse level with a soldering iron. Be aware that either way, once you have messed with your board, it will not have any core value for at least one of the reputable rebuilders that I know of.