95 LT1 compressor wont run, new compressor, full of freon, new pressure switch. Compressor will run by jumping the relay to ground, works fine. Hope someone has has this happen before.

 

I recently was in my AC system with a compressor that would not run...

I had a code for a shorted pressure sensor, that turned out to be bad re-pinning of the ecu harness.... anyway, I'm familiar now.

Do you have access to a scanner? If so, it will throw a code if the pressure sensor is bad. You can also check it for voltage, it should have +5v, gnd, and an analog line, should be 1v or so in open air if I remember correctly.

Anyway, if the pressure is incorrect, it will not allow the compressor to kick on. So, how did you get a system with a new compressor charged with freon without being able to run the compressor?

When mine was refusing to kick in, it would not take any r134a until we fixed the wiring issue with the pressure sensor.

 

If the low pressure code is retained in the PCM, it won't allow the compressor to come on. Reset the PCM to clear it.

 

+1 to Robs post above.. In response to post #2 . Low pressure cut off is about 20-25 lbs of refrigerant. An empty non running, vacuumed system should accept most of a 12 oz can of refrigerant which will pressurize the system over 25 lbs. Then by starting the engine & activating the A/C with no A/C DTC's the compressor should kick in and suck in the remaining refrigerant cans required to fully charge the system.