A/C died again on me a few days ago (perfect timing, it hit 96* today ), so I took it to the man figuring that there might be a leak in the system or something, no leak or anything. He said the problem was that the compressor wasn't getting any power. I checked all the fuses, and they are all fine. I tried to read the electrical diagram in the back of the Haynes manual to see if I could chase down where the fault in the system is, but I'm no electrician and I can't make heads or tails of the thing. What should I look at next?

 

When you press the A/C button, does the condenser fan come on? Does the engine rev up slightly?

Basically the ECU pulls in the compressor relay which then supplies power to the compressor from the 15 amp fuse under the hood. The same fuse runs the condenser fan.

 

The fan does not come on, nor does the engine rev up slightly. I'll check the 15 amp fuse under the hood.

If the fuse is OK, how would one check the compressor relay?

 

Fuse is fine.

 

Find the pressure switch, I think it is on the condenser though it might be on the drier. Measure voltage on either wire it should be near 12 volts with A/C off and drop to near zero with A/C button pressed. Test both wires. They should do the same thing if the switch is closed (presumably your mechanic checked and found the pressure to be normal, so the switch should be closed).

 

One wire reads 0V when off and 4.7V when on. The other wire reads 13.6 V whether the A/C is on or off. I'm looking for something that looks like a radiator fan switch right?

 

The switch should be closed circuit when there is normal pressure in the lines. Unplug the switch and check it for continuity. It seems it is open so check the pressure again, and if it is at saturation pressure for your temperature (about 100 psi in the summertime), switch must be bad. In order to replace the switch, the refrigerant must be recovered and then the system evacuated and recharged afterward.