2nd Gen Non-Engine/Transmission Here is the ac readings

[SAndreasen]

From my experience, The A/C readings you showed in the pictures indicate to me that either your compressor is not engaging, or it is drastcally low in charge. Now you have said that you had a shop replace the compressor, then you changed it. Did you add any refrigerant oil to it when you did the repairs? If you didn't put any oil in the system it will not function right. What I would recommend doing is to buy, rent, or borrow a refrigerant vacuum pump and put the entire system under a deep vacuum(as close to 29" to 30" as possible). Then let the system sit for about 10 to 15 minutes and see if the pressure rises. That will indicate a system leak. If it leaks tighten all fittings, replace seals accordingly and test it again. Once the pressure stops rising then add one can of oil charge followed by the correct refrigerant charge. Best way to do that with the gauge set you have is too hook up the refrigerant bottles to the main yellow hose and hook it up to the connection with the shrader valve. Than get a separate bottle tap and shorter hose and attach it to the connection without the shrader valve. Once the oil charge is in close the bottle tap valve and then open the refrigerant bottle tap valve and charge the refrigerant. This will both clear your lines and ensure all the oil gets in the system. Charge the system to normal level and see what happens, this should fix it. Hope this helps.

Thanks for the reply the compressor is not cycling if I supply power with my power probe I can make the compressor run and the system runs ice cold so I think the problem is electrical as far as the readings my Chevy has the identical readings and it blows cold also hooked the gauges up to the tractor and its high side readings are higher than ether truck and it also blows cold

 

[fest3er]

Since it works just fine when you manually apply power but is erratic otherwise, I suspect the PCM misbehaves.

Bypass the PCM. That is, take the PCM out of the clutch control circuit. Considering these engines don't have a problem climbing hills, there's no need for the PCM to disable the A/C to gain a couple ft-lb of torque. I believe the clutch power runs B+ -> dash control -> PCM -> low pressure switch -> high pressure switch -> clutch. (But that may be a ground circuit; I traced it once and posted it here some time ago.) Anything in the circuit can make the A/C not run. My PCM stopped running the A/C years ago; a local shop simply bypassed it. And clearly the PCM's relay--or relay control--can fail.

 

[SAndreasen]

Since it works just fine when you manually apply power but is erratic otherwise, I suspect the PCM misbehaves.

Bypass the PCM. That is, take the PCM out of the clutch control circuit. Considering these engines don't have a problem climbing hills, there's no need for the PCM to disable the A/C to gain a couple ft-lb of torque. I believe the clutch power runs B+ -> dash control -> PCM -> low pressure switch -> high pressure switch -> clutch. (But that may be a ground circuit; I traced it once and posted it here some time ago.) Anything in the circuit can make the A/C not run. My PCM stopped running the A/C years ago; a local shop simply bypassed it. And clearly the PCM's relay--or relay control--can fail.

Did they just run a seperate switch to control the compressor clutch? I'm considering replacing the heat ac control switch I've been studying the manual as my heater is not heating either and the manual says if the heat can't be controlled with the switch the switch is bad I've done all the other tests to check for plugged heater core . Sometimes I can turn the switch on and off for the ac and it will work and the heat does the same thing

 

[fest3er]

Did they just run a seperate switch to control the compressor clutch? ...

No, they ran a new wire from the PDC (A/C Clutch Relay, pin 85) to the wire before the low pressure cutoff switch (thus eliminating the PCM from the circuit). Everything else in the circuit is the same. And must be the same. You must have the high and low pressure cutoff switches in place to prevent/minimize damage to the compressor, and you must have the dash switch in place to turn A/C on/off. But you *could* put a separate switch on the dash in order to have chilled/dried air in all positions.

Looking at my '98 SM again, the stock circuits are:

• B+/fuse
• A/C clutch relay
• PCM A/C clutch relay control

and

• PCM A/C request sense
• low pressure switch
• high pressure switch
• dash heater control
• ground

The twerk is to connect the non-ground side of the low pressure switch to pin 85 of the A/C clutch relay in the PDC. That will maintain all of the necessary controls.

Turn the dash controls to an A/C position (defrost always selects A/C) in order to see (detect) the connection to ground. A ohm meter should show a short between pin 2 (ground side) of the low pressure switch and ground (key off, A/C position selected on dash control). And it should show open on pin 1 (PCM side) of the low pressure switch.

Verify that the A/C clutch relay in the PDC is OK. (Swap it with another relay.)

Jumper the PCM (non ground) side of the low pressure switch to pin 85 of the A/C clutch relay in the PDC. If A/C then works as expected, but returns to intermittent operation without the jumper, you can be certain that the PCM is at fault.

If that jumper changes nothing, you can then jumper the ground side of the high pressure switch to ground. If that works, the fault is in the circuit from there, through the dash control, to ground.

 

[SAndreasen]

Thanks for the reply. I have swapped the relay no change there is power at the relay can't tell you which pin tho it's been awhile since I've worked on it .ii will try the jumper