Like the title says, does changing the pressure switch (high side I guess) in the LT1's A/C system require draining the system, or does it have a schrader type valve below it allowing easy changing?


My A/C went out recently (had not been very cold for a long time, decided not to work at all now), and was throwing a low pressure DTC, so I put a can of r134a in the system and reset the comp, now the compressor comes on for a split second and the computer (via Datamaster) shows 350ish+ psi for that second, which would trigger the comp to shut off the compressor (it was showing 90ish psi before adding the can...). I'm wondering if the switch is bad, or if I have some other problem causing actual overpressure... Figure it will be fairly cheap and easy to change that switch and see if it's bad but only if I don't have to drain the system of refridge and refill...

Maybe all I did was overfill it, I had assumed it would only take as much as it needed though. I'm tempted to just drain a bit out...

Should I have to drain and pull a vacuum on the system, does anyone know if Autozone or Advance Autoparts or someone similar rents/loans a A/C system vacuum pump??

 

there is a shrader

however, I recommend first putting some gauges on it, look at the pressures

 

Thanks for the info. I would test the actual pressure, but I don't have access to any gauges and they seem kinda specialized and likely expensive, parts store didn't have anything in that area. I guess I should just take it somewhere and pay the money for a once over of the A/C system. I removed the pressure switch but the local quickie parts store wanted $75 for it and it may not have been the correct one, I was expecting $25ish...

Any way you or anyone else knows to trouble shoot this further without gauges?

Before even cranking the car, with the a/c compressor not having been run recently, what kind of pressure should the A/C system already be showing on the high side (if the pressure sensor were accurate)? It was something like 150-160psi a few minutes ago according to what Datamaster is reading from the computer.

After cutting it on and turning on the A/C and seeing the aforementioned spike, it slowly bleeds back down to 249ish and the compressor clicks back on for a split second spiking it again, and repeat. Does that sound like what it should be doing if there was a piece of debris or air in the system causing actual high pressure?