A/C compressor not turning on

OK, few thing i tested already is if the compressor clutch is working and it is, i tested it by jumping the one wire out of the compressor to my battery, and that tested good. second thing i tested is the A/C switch on the dash, continuity is there when i press on the switch. I also checked the relay next to the radiator and i have the 14 volts dc but not going through to the compressor. I tried taking the relay for the fan and switching it didn’t do anything. what else am i missing? Does the A/c pressure switch do anything?

Yes, it protects the compressor by cutting power to the clutch when refrigerant pressure is too high or too low. Do you have a full charge of refrigerant? If so the switch or wiring may be faulty.

would it be bad to short that switch so it would be on all the time. is it bad for the compressor to run when the pressure is too low?

:read:Yes, it would be bad. As mentioned, if the pressure is too high (blockage) or too low (o-ring deteriation/leaks), you need to have this checked. An oem o-ring kit is only $10 and an afternoon of putzing around. Most other diagnostics is preferably done by a certified dude.:slight_smile:

Ok i notice something now, I added more refrigerant in the system and my pressure switch shorted, compressor turned on and now I hear a hisssing sound coming from the compressor. Now evtsteward that o-ring kit your taking about, is that for the compressor? should i bother doing that or just find someone selling a compressor?

The oem o-ring kit consists of the 7 or so o-rings required to replace and stop any leaks around the piping. Your problem appears different. Just tossing info out. Still could have something plugged, which blew out the end seal of the compressor. Mine used to dwindle away in cooling over a six month period. Turned out to be leaks at the fittings around the engine bay.:dozing:

start by getting an o-ring kit. start with the easy ones ( the two on the compressor, and the two on the condensor ) then buy a qwik fill from walmart.
now your gonna want to drain the system first, use a screw driver and press down on the valve on the low pressure line ( the big hose ). then you can undo your fittings and replace the o-rings

I agree that it could be a leaking o-ring at the compressor manifold (or elsewhere), which caused you to lose refrigerant over time to the point that the pressure switch prevented the compressor from engaging. Another possible scenario is that you exceeded the safe pressure when you added refrigerant, causing the pressure relief valve on the compressor to open up. However, your pressure switch should have killed power to the compressor in that instance.

Did you take note of the pressure while you were adding refrigerant? I’m assuming you’re using a “quick-fill” kit of some sort, which aren’t always equipped with pressure gauges on the hose. Are you running R-134a?

I wouldn’t recommend that approach. I’d suggest you take it to a shop to have the existing refrigerant recycled instead. If you haven’t had a proper R-134a conversion done it would be a good time to flush the system and replace the drier (assuming you’re running or intend to run R-134a). I’d also replace every o-ring in the system while I had it apart. There are 2 o-rings each at the compressor, condenser, drier, and evaporator, and at every line fitting. So probably closer to 12 in total, iirc.

Of course, that’s all assuming best-case scenario (leaking o-ring or rings) rather than a bad seal in the compressor. Good luck!