1994 Truck Air Con Compressor Problem - Toyota Nation Forum : Toyota Car and Truck Forums

fc30 · 10-09-2006, 10:42 AM

In a 1994 Toyota Truck with 2.4L Engine, the Idle was running too low so we fixed it using one of the hex key settings on the throttle, but found that the Air Conditioning compressor goes on and off approx every 10 seconds. When the engine is in normal use, above idle, the compressor seems to stay on. But in idle, it turns on (bringing the idle speed lower) and soon turns off (the idle speed returns to normal but with no AC working). So at idle, the AC does not work well. Any thoughts?

Thanks in advance for your help...

johnyaya · 10-09-2006, 09:46 PM

If the engine is fuel injected then doesn't the computer regulate idle RPM? Just wondering what you turned and why it effected RPM. More important, was the AC working good before your adjustment?

fc30 · 10-10-2006, 10:50 AM

This problem was there before the adjustment, but less apparent because the idle was so low.

Everything I'm explaining is done when the AC button is in the On position.

Not sure why the compressor should ever be turning off automatically anyway, since that's controlled by the passenger. Perhaps there is something that disables the compressor when the idle is too low.

When the engine is first started, the compressor will not switch off improperly - it seems like the idle is high enough. It only seems to drop off (with a noticeable click) when the idle is lower. But in this case the idle is working fine and the compressor should not shut off. So whatever that device is might be the problem..

I suspect there may be some sort of vacuum or other device that needs to be replaced but not sure what devices are used to control the AC compressor..

Thanks..

johnyaya · 10-10-2006, 11:11 AM

I've got a 99 Tacoma with the V6. It's too cold right now to be running the AC, but the defroster uses the AC unit to dry the air. When the AC kicks on the RPM actually goes up a little. You mentioned vacuum, have you put a vacuum gauge on it to make sure there isn't a leak?

fc30 · 10-10-2006, 10:17 PM

No vacuum gauge but we could get one. Do you happen to know the correct vacuum level?

johnyaya · 10-11-2006, 10:05 AM

The correct vacuum depends on a lot of things. I would guess that at sea-level you should see something like 18 inHg. There are a couple of reasons why the AC compressor would shut-off automatically, if the high-side pressure is too high and I also think (but not sure) that there may be something for too low pressure. Have you put AC gauges on the system yet?

fc30 · 10-11-2006, 11:47 AM

No - how do the AC gauges work?

johnyaya · 10-12-2006, 11:38 AM

The AC gauge set has 2 gauges, one for the low-pressure (suction) side and one for the high-pressure (discharge) side. There are quick connect fittings on the AC system for connecting the gauges, but if you are not familiar with AC systems this may not help you much.

When the AC unit is switched on at idle the RPM should be raised slightly, but because yours drops you may need to first see if it's due to the AC compressor loading down the engine. There is usually an electrical clutch that is engaged when you want the AC compressor to run. I would look for that connector (on the compressor) and see if the engine RPM drops when you turn on the AC when the clutch is unplugged.

fc30 · 10-13-2006, 12:29 PM

The RPM is definitely dropping when the AC compressor starts. I don't see any sign of the RPM being turned up at that time. Perhaps that low RPM also causes the compressor to be automatically switched off, which is the main problem here. I will experiment with unplugging the clutch; that should be interesting. What controls when the clutch is turned on and off?