Compressor is always on even when the a/c button is Off. There is no difference between "on" or "off". I checked Freon and it has normal pressure on the Low hose. When I took the compressor out, there was no Freon in it or the hoses attached to it. The compressor costs about $450. I want to make sure I ruled everything out before buying a compressor. Thanks for your help!
Was the compressor making noise? If not, and you didn't use a full gauge set to check system pressures, you really don't have a basis for saying the compressor is at fault. It could well have been a problem with electronics or even the blend door not operating properly. Some compressors do not have a clutch and use an internal control valve instead so from the outside they appear to run continuously.
When you disconnect the compressor all of the refrigerant would have escaped into the atmosphere unless it has service valves which are not really used any more.
Now that the system has been opened up, at a minimum you really need to replace the drier as well when it is put back together. Also, the PAG oil used in AC systems absorbs atmospheric moisture like crazy and that moisture will not be released when pulling vacuum. (Moisture combines with the refrigerant to form acids that can eat holes in metal parts and cause leaks.) So if the system is left open for a long time it really needs to be flushed out and the correct amount of fresh oil installed.
Sounds like a hot mess, I'm afraid.
Agree its now a mess! Complicated A/C issues best left to the experts. Basic checks for the home mechanic.
For some reason a lot of people seem to blame the compressor first thing when they have AC problems. In reality if the compressor is not seized up or making noise and gauges show it is pumping there is no reason to remove or replace it. (I have a car here that's 50 years old and its original AC compressor is still pumping away.) This is probably one of the worst examples of using the parts cannon since there is collateral damage involved.
You didn't say if the A/C was blowing cold. If it wasn't, the low pressure switch shouldn't have allowed the compressor clutch to engage.
You also didn't say if you tried unplugging the wiring connector to the compressor to see if the A/C clutch disengaged.
$450 bucks is a hefty chunk of change.
It would be useful to know if the compressor clutch has mechanically failed
or if for some reason (pressure switch, faulty relay, ECU issue) the compressor clutch is getting power to engage when it shouldn't be getting power.
I'm hoping you had the system properly evaluated of refrigerant before pulling that compressor, it's highly illegal to vent refrigerant to the atmosphere, not to mention extremely dangerous. R134a is also a nasty greenhouse gas, if that's what the system came with. If there was a hissing noise when you unbolted and disconnected lines, there was refrigerant in the system. It's also not going to be liquid unless pressurized by the compressor and in the condenser. It's not liquid like motor oil at atmospheric pressure.
If there was no hissing, then the system was empty and you had a leak. I would have suspected damage to the condenser behind the grille as a first place to look on a 3-4 year old car. Road debris can easily hit and puncture it.
Don't take this as being mean, but please take the time to learn how air conditioning works before you blindly start tearing stuff apart. Most problems with them you can fix yourself with patience, the right tools and knowledge/ attention to detail. Your wallet, safety and the environment will thank you.
