I've had intermittent A/C failure on my 92 Civic DX going on for a couple years now. It's clearly an electrical problem. Normally it's solvable by putting some pressure on the control panel, but sometimes not. Once the system cools down (or dry out?), it seems to stay on well. I've recently done some diagnostics and determined:
- When the failure occurs, there's a voltage of about +3 to +9 volts between the blue/red wire out of the control panel (which runs from the A/C switch to the A/C thermostat and eventually the condenser fan relay and A/C clutch relay) and the vehicle body. When it's working, the voltage is +0.8 to +1.8.
- Making a connection from this point to the vehicle body (or any good ground) causes the A/C to come on, and then the compressor clutch engages and disengages as it should according to the A/C thermostat.
- The ground to the control panel has a voltage of +0.5 relative to the vehicle body, but it does not seem to be affected by whether the A/C or fan is on/off.
My best guess is that the connection inside the fan speed switch (which also acts as a master) or the A/C switch, or the wiring between them, is loose or corroded, but I haven't been able to figure out how to remove the control panel to open it up and test it without pulling off the air mix control cable for the heater, and it looks difficult to reconnect.
I'm looking for advice from someone who's experienced similar problems or has ideas for anything else I could try or how to easily take out the control panel. 'til then I'll keep shorting the blue/red wire to ground. :-)
Update: Is it possible this problem is caused by the infamous ICU capacitor issue?
I also have several other electrical issues going on: the headlight switch does not work reliably (I'm working around this by putting a jumper between the parking light and headlight fuses in the fusebox so that the parking lights turn on the headlights too) and the wipers sometimes don't work on intermittent mode. Also, some of the lights in the dashboard come and go at random.