Ac won't engage unless jumped at relay.
Jul 25, 2023 at 6:11 AM
A/C compressor not turning on?
2004 CHEVROLET SILVERADO
JASONMYERS360
- MEMBER
- 1 POST
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Hi,
When you jump the relay, does the AC provide cool air in the vehicle? I ask because if it is too low on refrigerant, the low-pressure switch will prevent it from turning on.
If it does work and you are sure the refrigerant is where it should be, we need to check at the relay (where you jumped it) to see if we have what is needed.
If you haven't already, switch the relay with a different one having the same part number to see if that allows the system to work. If it doesn't, I need you to remove the compressor clutch relay and do the following.
First, note there are four numbers on the relay identifying each pin. Numbers 85, 86, 30, and 87. Once you see them, determine which pin connects to each connector pin. First, check pin 30 for power. It should have power at all times (key on or off).
If that is good, check pin number 86 for power. This pin will only have power with the key in the run position. If that checks good, we need to check if the PCM is providing a ground pat top pin 85 when the AC is requested on.
Do this and let me know the results. Also, I attached the wiring schematic below so that you have a reference. I had to cut it in two to make it readable for you. I did overlap the two pics.
Take care and let me know what you find.
Joe
See pics below.
When you jump the relay, does the AC provide cool air in the vehicle? I ask because if it is too low on refrigerant, the low-pressure switch will prevent it from turning on.
If it does work and you are sure the refrigerant is where it should be, we need to check at the relay (where you jumped it) to see if we have what is needed.
If you haven't already, switch the relay with a different one having the same part number to see if that allows the system to work. If it doesn't, I need you to remove the compressor clutch relay and do the following.
First, note there are four numbers on the relay identifying each pin. Numbers 85, 86, 30, and 87. Once you see them, determine which pin connects to each connector pin. First, check pin 30 for power. It should have power at all times (key on or off).
If that is good, check pin number 86 for power. This pin will only have power with the key in the run position. If that checks good, we need to check if the PCM is providing a ground pat top pin 85 when the AC is requested on.
Do this and let me know the results. Also, I attached the wiring schematic below so that you have a reference. I had to cut it in two to make it readable for you. I did overlap the two pics.
Take care and let me know what you find.
Joe
See pics below.
Images (Click to enlarge)
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Jul 26, 2023 at 1:27 PM
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