AC wiring

[rocketmench]

Thank you LS1Nova! I've been a lurker for some years now as I plan my restoration project, and your posts are always helpful.

I set the A/C request mode to "Analog", I did not try "Analog Cycling". As I understand it, "Analog" mode requires a pressure sensor in the A/C line which controls a continuously running variable displacement compressor, as opposed to a simple pressure switch for the "Analog Cycling" mode which presumably uses a fixed displacement compressor that is switched on and off.

To emulate the pressure sensor with the appropriate pressure reading, you can either add a roughly 70-80 kohm resistor between I believe C2 14 and C1 45, which creates a voltage of about 2.5-2.6V at the C2 14 (the resistor acts as a voltage divider with the roughly 70kohm internal resistor at C2 14), or just directly input a voltage at C2 14. I did the latter.

As for difficulty level of the actual soldering, I was expecting worse. Using a basic soldering iron with a reasonably small tip, it was not too difficult to remove the one resistor, and add the necessary components. Taking care to use flux and basic good soldering techniques was all I needed. I did this on 2 pcm's without problems.

The coolest part was in observing Fan 1 come on a soon as I applied the 12V to C2 17 to request the A/C! Also, adjusting the potentiometer to change the emulated coolant temperature, I could cycle Fan 1 and 2 on and off at will.