The A/C on my 96 4Runner was working until a few days ago. I put the fan setting on auto, press the A/C button and a green light shows. The engine revs up a little. I took a look at the condenser while it was running and the drive plate is revolving fine and one line from the condensor runs hot when the A/C is on with engine running and the other line is at approx. ambient temperature. When it was working I recall that the revs would go up a little then down a little ever few minutes which no longer happens.

Any ideas?

Thanks

 

could there be a leak in the system somewhere? you may need to get the A/C system recharged.

 

Definately sounds like you lost your freon. Probably a bad seal somewhere. A decent A/C shop should get you up and running, but be prepared to shell out some $$.

 

The revs going up and down correspond to the magnetic clutch on the compressor engaging and disengaging. If the compressor ran non-stop, things would eventually freeze up, so it cycles on and off based on a temperature switch on the evaporator (I think).

as a first step, you can check to see if your magnetic clutch is getting power. There is 1 small wire going to your A/C compressor. Disconnect it, and measure the voltage between it and ground with the A/C switch off and on. With the A/C switch off, you should get 0 volts. With the A/C switch on, you should get around 12 V.