i've been through a lot and compressor wont come on

rdtavape · Jul 21, 2020

hello team! its been a while since i posted anything and i'm pretty sure i'm in a different car than the last time. anyhow. 97 gt just replaced everything having to do with the a/c let the vacuum pump run on it for an hour or so each time i have to open it back up. there's no leaking. the vacuum holds. i went so far as to swap the pcm cuz i saw a video where the a/c relay in the pcm was fried. nothing is making my problem go away. so here's the problem. my high side pressure will not go any higher than 100psi and the compressor won't come on. while charging the r134a the low side pressure builds up to about 100psi and so does the high side but won't go any higher and the compressor will not click on. i've also swapped the a/c switch thats up on the high side port near the condenser. does anyone have a little a/c knowledge they can give me some ideas? i've been stuck on this a/c for weeks and can't go without it. i'm in tucson az and its hotter than a mother up over here.

tsemmett · Jul 27, 2020

Without the compressor running, the charge should sit around the normal pressure for r134a for whatever the ambient temp is; 100psi sounds normal, so your issue is likely electrical.

Power for the compressor comes from fuse #6 under the dash, goes through the control panel, then to the low pressure switch, the high pressure switch, the CCRM, and finally the clutch coil on the compressor. On my 98, the ground for the coil is in an odd location too (driver's side rear of the engine up top).

I would grab a test light or multimeter (set to voltage), put the car in Run, turn the controls to AC or Defrost and test at three points: the compressor coil, the low pressure switch and the high pressure switch (between the dark blue/yellow and green/orange wires, the other 2 are for the fan). That should narrow it down like so:

If you have power at the compressor, your issue is either the compressor clutch, clutch coil, or the connector to the coil (I had one back a pin out and cause this).
If you don't have power at the compressor, and you do at the high pressure switch, you either have a short, or a bad CCRM.
If you have power at the low pressure switch but not the high pressure switch or compressor, you have a short.
If you don't have power at any of these points, it's either an issue with the ground, or with the power being supplied by the control panel/fuse.

If you let me know what you find, I can provide more detail.

rdtavape · Jul 28, 2020

tsemmett said:
Without the compressor running, the charge should sit around the normal pressure for r134a for whatever the ambient temp is; 100psi sounds normal, so your issue is likely electrical.

Power for the compressor comes from fuse #6 under the dash, goes through the control panel, then to the low pressure switch, the high pressure switch, the CCRM, and finally the clutch coil on the compressor. On my 98, the ground for the coil is in an odd location too (driver's side rear of the engine up top).

I would grab a test light or multimeter (set to voltage), put the car in Run, turn the controls to AC or Defrost and test at three points: the compressor coil, the low pressure switch and the high pressure switch (between the dark blue/yellow and green/orange wires, the other 2 are for the fan). That should narrow it down like so:

If you have power at the compressor, your issue is either the compressor clutch, clutch coil, or the connector to the coil (I had one back a pin out and cause this).
If you don't have power at the compressor, and you do at the high pressure switch, you either have a short, or a bad CCRM.
If you have power at the low pressure switch but not the high pressure switch or compressor, you have a short.
If you don't have power at any of these points, it's either an issue with the ground, or with the power being supplied by the control panel/fuse.

If you let me know what you find, I can provide more detail.

Thank you so very much! I finally got a call back from the senior tech at az auto refrigeration and he left me with his conclusion that it’s the ccrm but I’m pretty sure it’s not. Either way I swapped it with one out of my old mustang. So..... I will do the things u suggested and let u know what I find. Once again thank u so much.

i've been through a lot and compressor wont come on

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i've been through a lot and compressor wont come on

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