missthe1122
Member
- Joined
- Feb 16, 2011
- Location
- Long Island, New York
There are three components in play. The control unit, a servo motor which is wired only to the control unit and a power unit wired directly to the blower fan and also connects to the low pressure switch on the accumulator. The control unit works the vents flawlessly. I centered around the power unit that feeds the blower fan. This is what I found. The BLK wire from the power unit is GND with no voltage variation when running. There is a GRN/YEL wire from the power unit to one side of the low pressure switch on the accumulator. The fan wiring is VIO and BLU/BLK. Weirdness: Both of these wires have the full BATT voltage when running and when the car is turned off! That ain't gonna run a fan! And, why are they powered when the car is turned off? Looking at the terrible schematic I have from my Haynes manual, the Control Unit feeds the input to the Darlington pair transistor via A RED/BLK wire. It looks like a relay in the power unit switches the output of one of the transistors to GND. The other output of the transistor is wired directly to the BLU/BLK fan wire. I can't really understand how it works from the schematic. Anyway I don't believe it is a bad control unit, because I have two and they both do exactly the same thing and issue the same error code (233). I did open them up and look for solder problems, but a close inspection didn't show any. I believe the problem could be the power unit and of course I can't find another one of those. I believe this is the case because I measured full battery voltage in respect to GND on both fan wires when the engine is running and the engine is off. That can't be right. I can run the fan by disconnecting the BLU/BLK wire from the power unit and grounding it. What is going on?