A/C gurus, please come in...a/c wiring issue
05-10-2014, 12:53 PM
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A/C gurus, please come in...a/c wiring issue Quick run down of the issue.
When I purchased my car, 99 SS, the a/c worked fine, it cooled, came on when you asked it to and shut off under heavy throttle. Fast forward about 6 months and I noticed the a/c was starting to not kick on at idle when I started the car, however as soon as you got moving and the engine was under a load it would engage and cool.
Eventually the seals on the compressor crapped and I was having to add freon frequently for it to cool, all the while the compressor would not kick on at idle and only under a load.
I bought a complete kit to replace the system, compressor, dryer, orfice tube, etc. flushed the system out, pulled a vacuum down to around 28units and let it sit for an hour, no change in the reading.
I then purged the system, I had about half a can of freon still on my gauges, so I let it suck that in, and then vacuumed it back out and down to 28units again.
Then I put a fresh can of freon on the gauges and the system sucked in the can itself with out the car running. Fired up the car and the compressor would not kick on. If I jump the relay it will engage and cool, but as soon as I put the relay back, it kicks out.
I have tested the switch on the high side line and the 5volt reference is there, I also have power at the relay box, but not at the compressor when the relay is in, if I pull the relay and jump it, the compressor will click and the harness shows power at the plug.
At this point I am confused and pissed off, would a bad pressure switch cause these issues? The relay is good as I swapped it with another and tested it. All the wires seem to be in tact and where they need to be. Any input would be appreciated.
When I purchased my car, 99 SS, the a/c worked fine, it cooled, came on when you asked it to and shut off under heavy throttle. Fast forward about 6 months and I noticed the a/c was starting to not kick on at idle when I started the car, however as soon as you got moving and the engine was under a load it would engage and cool.
Eventually the seals on the compressor crapped and I was having to add freon frequently for it to cool, all the while the compressor would not kick on at idle and only under a load.
I bought a complete kit to replace the system, compressor, dryer, orfice tube, etc. flushed the system out, pulled a vacuum down to around 28units and let it sit for an hour, no change in the reading.
I then purged the system, I had about half a can of freon still on my gauges, so I let it suck that in, and then vacuumed it back out and down to 28units again.
Then I put a fresh can of freon on the gauges and the system sucked in the can itself with out the car running. Fired up the car and the compressor would not kick on. If I jump the relay it will engage and cool, but as soon as I put the relay back, it kicks out.
I have tested the switch on the high side line and the 5volt reference is there, I also have power at the relay box, but not at the compressor when the relay is in, if I pull the relay and jump it, the compressor will click and the harness shows power at the plug.
At this point I am confused and pissed off, would a bad pressure switch cause these issues? The relay is good as I swapped it with another and tested it. All the wires seem to be in tact and where they need to be. Any input would be appreciated.
05-11-2014, 11:19 AM
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From everything I've read I don't think there is a way to trick the switch, or the PCM into thinking it's seeing the correct pressure. In the end I swapped the switch and it works correctly again.