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Q: AC Switch/Temperature Control Module on 1999 Volkswagen Beetle

I have a major problem that my mechanic cannot figure out and I thought I would post this here. I'm on my 3rd Temp Control Module in 6 months. This is behind the dash and it controls the AC/HEAT and FAN switches. March 2009 was my first dashboard fire. Fixed by mechanic for $375.00. July 2009 AC switch began to ARC and melted the plug and wires. Car has been in the shop off and on since August 7 and today (Sept 9) a third module was installed and declared FIXED and it's not. While driving, the AC switch will turn itself on and off rapidly causing the compressor to make the engine miss heavily. Wiring has been heavily traced and switches replaced, but this doesn't fix the problem. Any suggestions anyone??? I LOVE MY CAR!! Nothing else is wrong with this beautiful Beetle!
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Hi, sorry to hear about your Beetle issues. What wires and which plug is overheating? Is the temp module overheating too?
The first thought I had when I saw your original question was that the blower motor may be causing the excessive amperage draw (excessive heat) at the Temp Control Module.
I've been looking at the wiring diagram for your Beetle, and the a/c switch seems to get it's power via the fan switch, which is tied to the heater blower motor. That is what I would take a good look at, have the mechanic check for excessive current draw from the blower motor and the blower motor resistor.
Just to be clear, without actually seeing your vehicle first hand, this is a bit of a guess, but there are only a couple electrical components that can cause this kind of heat buildup at the control head, and the blower fan is one of them.
Good Luck and you should have a fire extinguisher in your car at all times!
In March the Temp Control Module at the AC switch caught fire. In late July/early August the AC switch was on and the light behind the switch began to flicker and burn... no smoke... but you could smell the burning.

The mechanic said the AC switch in the Temp Control Module ... it's plug was melted down one side and the wires had to be replaced about 4 inches back. He also wrapped them and put a new plug in.

This didn't fix the problem and on Aug 7 the car was returned. The AC switch will turn itself on and off either staying on or rapidly going OFF and then ON making the engine miss or kick due to the rapid on and off of the AC compressor.

They dug in once more and "thought" that the problem secondary was a Thermal switch. Not so. The car was again returned to the mech and they kept it until today. They decided to trace the wiring over the last 7 days. Found no shorts or exposed wires... replaced the Temp Control Module and called it fixed. Picked it up today and it's still doing the same thing.

On the drive home, the AC switch turns itself on and stays on no matter if you turn it off by pressing it in or out, or by turning the fan switch off (to ZERO).

Sorry for the longer answer. The module seems to be overheating again and we're at a loss right now. I certainly don't want another dash fire.
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