a/c question (i know i've seen it before, but i can't find it)

[turboranger91]

my compressor doesn't engage. the blower motor is still in good working order and i'm sure the system will need a charge, but the compressor won't turn.

now, i'm sure that what i'm supposed to do is take out one of the shims on the compressor. where is the write up on that?

 

[naval-avi8or]

It won't turn or the clutch just isn't engaging?

 

[turboranger91]

It won't turn or the clutch just isn't engaging?

the clutch isn't engaging.

 

[naval-avi8or]

Low Charge, Bad cycling switch, bad clutch, clutch needs airgap shim removed no power to clutch.

SET AC TO MAX AC FOR TESTING
1. disconnect cycling switch and jumper electrical connector.
Did compressor kick on
Yes - Check freon charge, service as needed and replace cycling switch
if froen service doesn't fix.
No - Check for 12V at AC compressor connector

2. diconnect ac compressor electrical conector check for 12 volts.
Yes - Check resistance of AC clutch coil (resistance not OK replace
clutch, resistance OK remopve Shim)
No - Check CCRM input and output for AC clutch signal voltage.

3. Check for voltage output from CCRM to clutch @ CCRM
Yes - service open wire between clutch and CCRM
No - Check for Signal inout voltage from PCM.

 

[turboranger91]

Low Charge, Bad cycling switch, bad clutch, clutch needs airgap shim removed no power to clutch.

SET AC TO MAX AC FOR TESTING
1. disconnect cycling switch and jumper electrical connector.
Did compressor kick on
Yes - Check freon charge, service as needed and replace cycling switch
if froen service doesn't fix.
No - Check for 12V at AC compressor connector

2. diconnect ac compressor electrical conector check for 12 volts.
Yes - Check resistance of AC clutch coil (resistance not OK replace
clutch, resistance OK remopve Shim)
No - Check CCRM input and output for AC clutch signal voltage.

3. Check for voltage output from CCRM to clutch @ CCRM
Yes - service open wire between clutch and CCRM
No - Check for Signal inout voltage from PCM.

i'll check these first and then try removing a shim.

 

[NoSlo]

Pretty simply, if you have a low refrigerant charge, the AC system won't turn on.

The AC system is pretty simple: a pressure sensor (the 'AC cycling switch') is located on the low pressure side, and engages the A/C compressor clutch if the pressure at the sensor is above 40-47psi. The compressor then runs until it has pumped the pressure down to 22-28psi on the low side. After that the compressor turns off until the coolant slowly passes through the orifice valve seperating the high pressure from the low pressure side. Once the pressure goes back up to 40-47psi, the compressor turns on again. The normal operation is that the system cycles on and off (the normal cycle time depends on the ambient temperature). If the refrigerant charge is low enough that the pressure of the whole system without the system running is not above the PSI where the switch turns on, the system won't ever run. [As a side note, if the ambient temperature is below about 50 degrees, the system won't turn on because the system pressure is naturally too low at low temperatures; the heat of the engine may warm the AC tubes up enough that it will still turn on after a while in cold weather though.]

You can jumper the AC cycling switch plug to simulate a pressure switch that is on - that should make the system run and you can see that everything else is working, but it sounds like you have a leaky system that needs to be converted over to r134a after all the O rings are replaced and the system is flushed out. If you recharge the system up with expensive and hard to find r12 it will probably just slowly leak out again and be bad for the ozone layer too.