Air-con issues
Thread Starter
Teching In
Joined: Jun 2018
Posts: 8
Likes: 0
Air-con issues Hey guys, been lurking here for a while, but finally decided to post. Some of y'all are wizards lol!
Anyway, I just picked up a 95 formula 6 speed, my first fourth gen, but is firebird #12 hah. All the rest have been third gens, including my current 92 and 91.
Anyway, this thing is mostly stock, minus an MSD optishart, longtubes, CAI, and a cat delete, and in fairly decent shape. The AC was inop when I bought it.
Alright, pulled the jumped the compressor, works fine. Replace relay, no change.
Then checked pressures while running via jumping the compressor, all looked fine. Was around 38 on low side, 220 high side. Had a slight leak on the low side valve core, so I evacuated the system, replaced the part, vacuumed it and charged back to the same pressure. Still no ac..
So, I reset the pcm. Success! Ac compressor kicks on on it's own. For like 5 minutes. Then stays off until next reset. That's where I'm stuck at. I ordered an aldl cable for it, still in the mail, tho. Meanwhile it's 102° today. When it does kick on, it gets cool.. but not cold. Only slightly cooler than my r134 converted 91. The fans do kick on, though.
Something else I've noticed, is that when the AC compressor is on after a reset, when I go to drive, sometimes when I stop, the voltage in car drops to around 10. Which makes me think it's either the compressor itself is shorted..or the pcm has an issue? Wont know for sure till i can get a computer hooked up here. Any advice on this?
Anyway, I just picked up a 95 formula 6 speed, my first fourth gen, but is firebird #12 hah. All the rest have been third gens, including my current 92 and 91.
Anyway, this thing is mostly stock, minus an MSD optishart, longtubes, CAI, and a cat delete, and in fairly decent shape. The AC was inop when I bought it.
Alright, pulled the jumped the compressor, works fine. Replace relay, no change.
Then checked pressures while running via jumping the compressor, all looked fine. Was around 38 on low side, 220 high side. Had a slight leak on the low side valve core, so I evacuated the system, replaced the part, vacuumed it and charged back to the same pressure. Still no ac..
So, I reset the pcm. Success! Ac compressor kicks on on it's own. For like 5 minutes. Then stays off until next reset. That's where I'm stuck at. I ordered an aldl cable for it, still in the mail, tho. Meanwhile it's 102° today. When it does kick on, it gets cool.. but not cold. Only slightly cooler than my r134 converted 91. The fans do kick on, though.
Something else I've noticed, is that when the AC compressor is on after a reset, when I go to drive, sometimes when I stop, the voltage in car drops to around 10. Which makes me think it's either the compressor itself is shorted..or the pcm has an issue? Wont know for sure till i can get a computer hooked up here. Any advice on this?
TECH Fanatic
Joined: Dec 2017
Posts: 1,476
Likes: 271
From: Bossier City, Louisiana
My chart shows a required low pressure number for 100 degrees F as 50-55 PSI running R134A. Sounds like you might be undercharged. Don't forget to add some compressor oil of whatever type is required for your system.
I had to add a can to the AC in my 99 F-150 truck yesterday. Made a lot of difference going from about 40 PSI on the low side to 50 PSI and I'm certain my condenser of much better saturated now.
Rick
I had to add a can to the AC in my 99 F-150 truck yesterday. Made a lot of difference going from about 40 PSI on the low side to 50 PSI and I'm certain my condenser of much better saturated now.
Rick
Thread Starter
Teching In
Joined: Jun 2018
Posts: 8
Likes: 0
My chart shows a required low pressure number for 100 degrees F as 50-55 PSI running R134A. Sounds like you might be undercharged. Don't forget to add some compressor oil of whatever type is required for your system.
I had to add a can to the AC in my 99 F-150 truck yesterday. Made a lot of difference going from about 40 PSI on the low side to 50 PSI and I'm certain my condenser of much better saturated now.
Rick
I had to add a can to the AC in my 99 F-150 truck yesterday. Made a lot of difference going from about 40 PSI on the low side to 50 PSI and I'm certain my condenser of much better saturated now.
Rick
My quick guess would be to look at the pressure sensor. Not sure what tests they have, but it's a 5 volt pressure sensor and if it reads 0 on the output it's dead as the range is 0.5 to 4.5 or 0.5 to 5 on all of them. I'm thinking the reset gets it to ignore the bad signal until it confirms it.
Thread Starter
Teching In
Joined: Jun 2018
Posts: 8
Likes: 0
My quick guess would be to look at the pressure sensor. Not sure what tests they have, but it's a 5 volt pressure sensor and if it reads 0 on the output it's dead as the range is 0.5 to 4.5 or 0.5 to 5 on all of them. I'm thinking the reset gets it to ignore the bad signal until it confirms it.
It's not currently 90deg out..so that seems sensor is inop, but should allow the air-con to still work-just might freeze up the evaporator.
Sweet. Take it for a drive, sure enough it shuts the AC off. The only dtc was for code 61, which looks to be just a generic "ac system performance".
That's..it.
