Ac issue

powerstrokenstang · May 18, 2015

Got a guys truck that ac clutch wont engage. Fuse under dash is good but doesn't send power to clutch. Any ideas? Has good static charge

HOOV3R · May 18, 2015

Pressure switches working correctly (closed)?

Magnum PD · May 18, 2015

One is open when under pressure, and the other opens if over pressured? Make sure current is getting to both switches.

Garbage_Mechanic · May 19, 2015

The low pressure switch on the accumulator (black tank by the AC box) can be temorarily bypassed with a paper clip to see if is is the one holding the clutch from engaging. It is open with low pressure in the system (low charge) It seldom fails so if it is open it is likely low charge in the system. Use a guage set or have someone check the freon pressure.

The high pressure switch on the compressor opens if the pressure goes too high because of low air flow, clogged orfice or overheating of the AC system.
I have had a lot of problems over the years with the engine vibration loosening the pins in the plug going to the high pressure switch. Causing an open circuit, no clutch engage. It can also be temporarily bypassed to test. Replacement plugs are available.

OBS-Addiction97 · May 19, 2015

Garbage_Mechanic said:
The low pressure switch on the accumulator (black tank by the AC box) can be temorarily bypassed with a paper clip to see if is is the one holding the clutch from engaging. It is open with low pressure in the system (low charge) It seldom fails so if it is open it is likely low charge in the system. Use a guage set or have someone check the freon pressure.

The high pressure switch on the compressor opens if the pressure goes too high because of low air flow, clogged orfice or overheating of the AC system.
I have had a lot of problems over the years with the engine vibration loosening the pins in the plug going to the high pressure switch. Causing an open circuit, no clutch engage. It can also be temporarily bypassed to test. Replacement plugs are available.

I've had my low pressure bypassed for some time now. If I wiggled the switch itself it would stay one temporarily, same scenario with a different switch. I'm not sure what the issue is, I don't believe I have a low charge it's gets below 40* in the heat of summer in Fl.

Patrick Feeley · May 19, 2015

I had problems with the connector pins on the compressor-mounted switch as well. I just worked them a little to provide a tighter fit to the other pins. Cheers!