Any A/C Experts in here? Odd A/C pressures..
Any A/C Experts in here? Odd A/C pressures.. I have a 1970 Chevelle with a vintage air kit installed. The AC worked great all summer. A couple weeks ago, I drove a 2 hour trip in Houston summer heat (heat index was about 108 degrees). AC worked perfectly the whole time. I got home, and parked it, not to drive it again until yesterday. That is when I noticed the AC wasn't blowing cold anymore.
I heavily inspected the lines, and there is no evidence of it leaking. These are the pressures I'm getting
Car on/AC compressor running
Low side: 8 inHG (yes, it is in vacuum)
High Side: 80 psi
Car off/AC compressor off
Low Side: 35 psi
High Side: 35 psi
I have a binary switch, that should shut the AC compressor off in the presence of low freon. The AC compressor is still on.
One thing that is really weird is my friend who has the same setup, went to the same show in his car - and after the show his AC stopped blowing cold also.. he thinks the pressures got to high, but idk - the binary switch should handle that and safeguard everything. Maybe pressures were so high it created a leak? I did notice when I unscrewed the high side port cap, that I heard a small little hiss noise like pressure was held in by the cap.
I heavily inspected the lines, and there is no evidence of it leaking. These are the pressures I'm getting
Car on/AC compressor running
Low side: 8 inHG (yes, it is in vacuum)
High Side: 80 psi
Car off/AC compressor off
Low Side: 35 psi
High Side: 35 psi
I have a binary switch, that should shut the AC compressor off in the presence of low freon. The AC compressor is still on.
One thing that is really weird is my friend who has the same setup, went to the same show in his car - and after the show his AC stopped blowing cold also.. he thinks the pressures got to high, but idk - the binary switch should handle that and safeguard everything. Maybe pressures were so high it created a leak? I did notice when I unscrewed the high side port cap, that I heard a small little hiss noise like pressure was held in by the cap.
TECH Fanatic
Joined: Dec 2017
Posts: 1,469
Likes: 267
From: Bossier City, Louisiana
I think I would try a can of refrigerant and see what happens - usually $4.88 around here at Walmart. Though you might get a can with some compressor oil in it (more money) but make sure its compatible with the oil already in your system. You have little to lose here except a few dollars because your pressures do not indicate that you are overfilled. Just remember - don't fill your system with the refrigerant can upside down. This allows liquid refrigerant into your system and it is not compressible which is tough on things in your compressor.
Refill your system using the commonly available temperature vs pressure charts on the Internet. For me around here on a hot 90 degree-ish afternoon, I look for 50 PSI on the low side and 260 PSI on the high side. R134 refrigerant, of course.
Rick
Refill your system using the commonly available temperature vs pressure charts on the Internet. For me around here on a hot 90 degree-ish afternoon, I look for 50 PSI on the low side and 260 PSI on the high side. R134 refrigerant, of course.
Rick
