A/C Clutch not cycling ie turning off

[davetexas]

90 GT, Has R12, system was recharged about 10 years ago with new dryer.

When I turn the A/C on the clutch comes on and the A/C cools extremely well but the clutch does not turn off or cycle. It will turn off if I turn the ac switch off.

I would think it should cycle on and off? Any suggestions or Ideas?

Thanks!

 

[Noobz347]

Working from a vague memory here and it's been a while so bare with me:

There's a box behind the passenger side dash that contains the thermal switch (up against the plastic face between the vents). Some (I think) have an adjustment dial while others did not (depending on year). If yours has an adjustment dial, give that a shot first. You should be able to set the tempurature cut-off threshold with that dial. If there's no dial then you may need to break that little box open to inspect/clean the contacts. Short of that, the box may require replacement.

Prior to opening the box though... you should be able to manually open and close that circuit with a metal clip or wire to ensure the circuit is working.

 

[davetexas]

Could it be the pressure switch? I really don't want to have to evacuate the system

 

[Noobz347]

Based on your description? No. If your system was low on pressure then the clutch would not engage at all.

 

[HISSIN50]

You should not need to discharge the system to remove the LPCS.

Do you have gauges? See what the pressures are (esp the low side). If it's low but the LPCS is not cutting out (the switch is stuck in the closed position), test the switch and replace it if needed.

It's possible to charge the system enough to where the clutch does not cycle.