Hi,
My daughter returned her 92 940 and I'm whipping it back into shape. The AC quit working late last summer. I did some quick diagnosis this morning. Doesn't look like current is getting to the pressure switch on the accumulator. If I jump power to the compressor, the clutch kicks in.

So a couple of questions. I've looked around the brickboard and couldn't find answers to these but could have missed something.
1) Should the AC be on when defrost is turned on and the "AC Off" button is out?
2) Is the electrical path 12 volts from the climate control unit to the pressure switch on the accumulator and then on to the compressor?
3) How likely is a failure in the climate control unit? I saw some notes in the FAQ about replacing the AC relay. I also have a spare climate control unit I can put in if needed.

Thanks!
Lyle

Hello,

I'm assuming that your AC fuses (#6 and #16) are ok, your blower is functioning and yours is the manual climate control box (without the AUT - automatic selector).

To answer your questions:
1. For the compressor to run (means 12 volts to the pressure switch) the blower speed must be set to at least position 1 and AC button ON. I don't use the defrost option (living in hot climate) so I can't be sure, but why not use the usual AC settings - vent to face and temp selector to coldest.

2. Yes and no. Yes in that sequence, if your AC has not been added with high pressure cut-off switch. No if this switch has been added, this means - control box --> low pressure switch (accumulator) --> high pressure switch --> compressor. On late model 940 this high pressure switch is on the condenser (purple switch). On earlier 940 add-on version this switch may be on the high pressure pipe leaving the condenser.

3. With no 12v from the control box its failure is most likely (provided you've fulfilled the conditions at the topmost and below). The AC relay itself rarely fails. Its contacts are sealed in nitrogen filled space (long lasting). Only its solder connections needs to be reflowed.

One more important thing to check...if your car is using the resistor blower pack located at the blower housing then check its lowest electrical connector (the one with 4 wires) for good contact as this is the grounding point for the AC control box. Poor grounding means no functioning box and no 12v (the blower might still work though).

Hope this helps,
Amarin.

That is what I needed. Thanks so much!