I hung out with a friend today to help him finish up an AC compressor replacement in a 2005 Mazda3. It seemed like it was going well, aside from some tool issues, until we hit a snag. His description:
My notes: - We charged the system through the low side while the car was running with AC on (compressor engaged) up to ~45-50 PSI as measured by a cheap gauge/hose combo that screws onto the top of the R134A cans you get at auto parts stores. The AC was blowing cold when we were finished. - While on a drive with the AC running is when it started blowing warm again, and we got the smell he referred to. The smell could've just been spilled oil that finally got hot enough to burn off but the timing was quite coincidental if that's the case. - The "150 PSI" refers to checking the pressure using the same gauge, from the low side, after the car was shut off. I'm not clear on why the pressure read higher after the car shut off or whether that's a problem. But we tried on another car with working AC and got a similar reading, so maybe it's either normal or the gauge is screwy? Is the most likely scenario a clogged expansion valve due to debris from the old seized compressor? The only other possibility that comes to mind is an electrical problem but that seems less likely to me. I'm hoping for his sake that replacing only the compressor wasn't too big a mistake.
The AC in my 2005 Mazda 3 stopped working 6 months ago. Finally got around to working on it: replaced the high pressure hose, then realized the compressor had seized. Just finished putting the new compressor in. I cleaned the system with solvent and put it under -30psi vacuum for ~an hour. Then charged it up, and it worked great! For about ten minutes. Then the AC started fluctuating in temperature from room temp to cold. Then I got a burning smell and it stopped cooling. The AC clutch is not engaging now. The low side of the ac was at 50psi when I charged it, and it's at ~150psi now (but the car is hot). Any ideas? I'm thinking it might be a stuck expansion valve. There was a bit of metal in the oil from the old compressor.