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Howdy,
I thought I would share this with the board.
The temperature selection dial on the MCC (which operates the distribution shutter servo motor behind the glove compartment) was dead. Aside from regulating the mix of hot and cool air, the knob allows the A/C to work only when it is in the full cold or CCW position.
Per the FAQ, I took out the MCC circuit board and looked for a poor solder connection holding the built-in relay, or anything that resembled a broken solder joint. None found. Dejected, I looked all around the board with a magnifying glass and then found the very small section of burnt out / broken wire, circled in red in the attached image (if it uploads).
I traced the destination of the wire and found it to come from pin #1 on the MCC and leading to a solder connection for some little resistor (or something) and then into the labyrinth of connections within the circuit board. Multimeter proved there was no continuity between the 2 points.
In the green wiring book, pin #1 appears to have no direct connection to the servo motor control the shutter for air temp, but it ultimatly connects to ground. Anyhow, I am no electronics guy but I had nothing to lose and already had everything apart.
I took a single copper filament from a wire and soldered it at each end to where the burnt wire was leading, marked "bypass" on the image. Mulimeter now showed good continuity between the 2 solder points.
Imagine my surprise when I put it all back together the MCC works perfectly!
I encourge anyone to try this with these contol units that most mechanics replace without a second thought.
Al
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