What to do if your AC compressor relay is not grounding?
But before splashing $100 on a replacement PCM you better be DARM sure the relay control ground wire is making contact with the above mentioned pin on the PCM. You can always use a meter to check if the PCM is working. Just connect one probe of the meter to the battery positive voltage and the other to pin 27 of the PCM.
Where is the relay on an AC compressor?
Basically when applying + to C3 (from the Cruise Fuse thorough the serially connected pressure switches) and (-) to the D1 pin (from pin 27 on C1 connector of the PCM – software algorithm) the relay closes the contact between pin D3 (from the A/C fuse – ORN wire) and pin C1 (to the A/C Clutch – DK GRN/WHT wire) engaging the compressor.
How is the a / C relay connected to the ground?
This input is connected to D1 pin of the A/C relay via a DK GRN/WHT wire. It is exactly the pin you connected to the ground by bypassing the PCM. Now since you say the A/C kicks in the both your A/C Low Pressure and your A/C High Pressure Switches are closed (as in the refrigerant pressure is fine).
How does the PCM control the AC compressor relay?
Also whit the switches closed (i.e. pressure OK) the PCM controls the relay via pin 27, closing the relay contacts (thus engaging the A/C clutch) when command received as long as the engine is in the proper RPM range.
But before splashing $100 on a replacement PCM you better be DARM sure the relay control ground wire is making contact with the above mentioned pin on the PCM. You can always use a meter to check if the PCM is working. Just connect one probe of the meter to the battery positive voltage and the other to pin 27 of the PCM.
Basically when applying + to C3 (from the Cruise Fuse thorough the serially connected pressure switches) and (-) to the D1 pin (from pin 27 on C1 connector of the PCM – software algorithm) the relay closes the contact between pin D3 (from the A/C fuse – ORN wire) and pin C1 (to the A/C Clutch – DK GRN/WHT wire) engaging the compressor.
What causes an AC compressor to not engage?
If the clutch doesn’t engage, the problem could be a blown fuse, an open in the wire to the clutch coil, a bad clutch coil, a poor ground, or a low pressure lockout. AC compressor clutches receive power in a number of ways. They can activate through a relay that’s energized directly by a proper condition of the low and high pressure switches.
This input is connected to D1 pin of the A/C relay via a DK GRN/WHT wire. It is exactly the pin you connected to the ground by bypassing the PCM. Now since you say the A/C kicks in the both your A/C Low Pressure and your A/C High Pressure Switches are closed (as in the refrigerant pressure is fine).
Also whit the switches closed (i.e. pressure OK) the PCM controls the relay via pin 27, closing the relay contacts (thus engaging the A/C clutch) when command received as long as the engine is in the proper RPM range.