I was working on a 2000 Nissan Xterra SE (standard trans) 3.3L V6 (VG33E) engine with approx 160,xxx miles originally from the Midwest US and now in the Southwestern US. I discovered that the AC system would work when I charged it up with FREON and blew cold for about 2 weeks on a cross country road-trip. The AC system started to blow hot air and I decided to leave it alone for about 2 years
Recently, on a particularly hot day, I decided to recharge the system with FREON and the AC system blew cold for about 1-2 days. I noted that the pressure on the low side would go down so I thought there might be a leak. I used FREON with UV dye and located the leak at the high-pressure line connecting the compressor to the condenser. I replaced the line and the accumulator/drier and pulled a vacuum. The system held at about 20 hg with the pump and system off. When disconnecting the gauges, a hissing and air was felt and heard from both high and low ports.
I decided to fill the system with FREON anyways but that was a major mistake. With about 50 PSI from a 12oz can in the system at the low port and the AC running on full blast and blowing cold air, I disconnected the FREON from the charging port only to have the FREON discharge at me.
Since I lack common sense, I decided to run another vacuum then refill the port with FREON but did not disconnect the gauge from the port. The pressure maintained but then dropped so I filled more FREON into the system with a total of about 16-20 oz in the system and PSI at 50. The system ran fine for about 2-3 days with cold air blowing. I checked the gauge and the reading was at about 15 PSI with the cold air on high. I decided more oz FREON into the system with pressure going up to about 20 PSI then dropping back down to about 15 PSI. The gauge started to hiss and a small amount of FREON dripped from the hose. I promptly stopped everything.
What could be going on with the pressure in the system? Could something be clogged in the system, and if it is, where could it be? I already suspect I might have not put the line on properly and am planning on redoing the line soon. I want to know if it might be the condenser or the evaporator or if I might have ruined my compressor
The compressor would have cut out when the low side pressure dropped below about 20 psi unless you shorted the low pressure safety cutoff, so compressor is probably OK if it was to begin with.
It sounds like you have leaks out the wazoo going on there. It's also quite possible on a vehicle that old the evaporator could be leaking and you're not going to see with dye that since it's buried in the dashboard. You'll need an electronic detector for that.
What was the high side pressure doing during all of this?
Thanks Chuck Tobias,
I am hopeful that my ac compressor was able to save itself as you mentioned. I'll look up one of those electronic detectors - I had no idea that existed - and look up that low-pressure safety cutoff you mentioned just to make sure the whole system works.
For the high-pressure side, the pressure was at about 180hg when I initially filled the system with refrigerant. Thereafter, I did not check it even though I should have, so that's a lesson learned. I think Scotty did make a video about the AC system's high-pressure side being too high vs too low and the low-pressure side being too low vs too high and what those symptoms can suggest, so I think I should go review it.
I failed to mention but I did try to look down under my dash to replace my cabin air filter only to see there is no cabin air filter so maybe the evaporator is old and damaged from years of dust and abuse like you suspect.
Thanks again Tobias, I actually was suspecting the condenser more than anything but I think your evaporator theory makes more sense.