I recently purchased a '91 4R (acutally it's a Hilux Surf bought here in Japan). Just over a year ago, the A/C system was recharged and the receiver/dryer replaced. Here is the problem:

If the fan is in any other position except off, the compressor clutch engages and it blows cold air with or without the A/C button depressed.

More specifically:
With the fan running, pressing the A/C button (i.e. A/C control switch in the on position) will cause the motor to idle higher, the green light will come on and obviously the compressor turns. Air blows cold.

With the fan running, depressing the button (i.e. A/C control in the off position) will cause the idle to drop, green light turns off but the compressor still turns. Air blows cold.

Fan switch off causes the compressor clutch to disengage and the green light on the A/C control switch goes out (regardless of button position). Obviously no air at all is blowing.

I'm thinking it could be a compressor coil issue as the switch inside the cab actually still kicks the idle up when activated and the green light comes on so it seems to at least partially work as advertised.

I took the dash apart hoping to be able to remove and test just the A/C control switch but of course it's part of the whole environmental control assembly which appears to be a complete pain in the ass to remove as a unit.

It's not a huge problem, but as the cooler weather is approaching I like to have the fan running blowing external, ambient air instead of running the compressor all the time.

Any thoughts or suggestions?

R/
Konish

A simple cure would be to unplug the wire for the compressor clutch. Then it won't go on at all.

1: is it set to defrost? some systems turn the air on to help clear the windshield when set to defrost.

2: does it blow hot air when the temp is set to hot even if the air is turned on, it should.

that's all I have, good luck with it.

Actually, it might. And if it does, the problem is probably a seized compressor clutch.

If the compressor clutch was seized, I wouldn't think it would turn off (disengage) when the fan is off. In other words I can get it to engage or disengage simply by turning the fan on and off. The A/C switch does nothing in terms of the compressor clutch.

It is in regular A/C mode (i.e. not in defrost) and it does blow hot air when it is selected on the temp control.

On a guess, I'm wondering if the A/C control switch is grounding that curcuit all the time regardless of switch position allowing the compressor to run continuously...?
If that's the case, should I not then be seeing continuity on the circuit regarless of switch position(?)

The real question is replacing the environmental control unit...I don't think it's going to be fun or easy I'm guessing.

R/
Dustin

See what happens if you pull the fuse for the AC...