Correct AC Pressure
Thread Starter
Racer
Joined: Nov 2006
Posts: 264
Likes: 8
From: Centre, AL
Correct AC Pressure
What is the correct AC pressure at about 84 ambient?
Currently mine is about 28 with the fans running, and 32 without the fans on the low end and 200 with the fans and 250ish with the fans off on the high end. Temp inside is about 48 center and side. 1000 rpm
Will check again if these pressures seem a bit off, just what I can remember from memory.
How should you measure? Fans off or on?And then what viscosiy PAG oil does GM use for the vettes?
Currently mine is about 28 with the fans running, and 32 without the fans on the low end and 200 with the fans and 250ish with the fans off on the high end. Temp inside is about 48 center and side. 1000 rpm
Will check again if these pressures seem a bit off, just what I can remember from memory.
How should you measure? Fans off or on?And then what viscosiy PAG oil does GM use for the vettes?
Last edited by waterzap; Jul 23, 2007 at 10:13 PM.
Burning Brakes
Joined: Apr 2007
Posts: 966
Likes: 9
From: Phoenix AZ
Okay, so I'm guessing mine is overfilled...I checked it with a cheap gauge from Autozone and it read close to 55 psi on the low side. Ambient temp was probably close to 115, though, and the engine was hot. Does this sound right?
Thread Starter
Racer
Joined: Nov 2006
Posts: 264
Likes: 8
From: Centre, AL
Get a decent guage with hight and low presure, and keep the engine and fans running while testing.
This is one of those things that if you decide toi do it yourself, which will save and empower you in the long run, you have to do it right or it could cost a lot to fix. How do you capture r134, since it is illegal to vent ? Is there a container you can get? And what do you do with it afterwards ? I have taken coolant to Pepboys, but not sure if they will siphon off gas and give me back my container....i
This is one of those things that if you decide toi do it yourself, which will save and empower you in the long run, you have to do it right or it could cost a lot to fix. How do you capture r134, since it is illegal to vent ? Is there a container you can get? And what do you do with it afterwards ? I have taken coolant to Pepboys, but not sure if they will siphon off gas and give me back my container....i
Last edited by waterzap; Jul 24, 2007 at 08:11 AM.
Melting Slicks
Joined: May 2000
Posts: 2,498
Likes: 4
From: Brentwood TN
Charlie
Pro
Joined: Jun 2007
Posts: 631
Likes: 3
From: Joppa AL
This seems to be a recurring question so I'll throw in my 2cents. Here is a chart I've had taped to my shop wall for many years and it's served me well. Couple of caveats here:
Humidity affects press more than temp.
All readings are at 2000rpm
You will never see these exact readings as there are many other factors involved. The test port location on the hose can change the reading. Close is OK.
The only real danger is too much high side pressure. BE CAREFUL! There are a lot of things that can generate too low a reading on the low side other than insufficient refrigerant (restriction in orfice tube, dirty evap, etc, etc.) If you charge w/o a high side gauge under these conditions you may go way over on the high side and damage your car and/or you.
Also remember, the longer you run the car in the shop the higher the press will creep. Just like eng temp. There's nothing real exotic here compared to some issues I've seen discussed on this board, but there are some safety issues. One last thing, a high side hose connection blowing apart while you have your head under the hood could cause a massive cardiac arrest for old guys like me. Don't ask me how I know this. As always, JUST MY OPINION, OTHERS MAY DISAGREE.
Humidity affects press more than temp.
All readings are at 2000rpm
You will never see these exact readings as there are many other factors involved. The test port location on the hose can change the reading. Close is OK.
The only real danger is too much high side pressure. BE CAREFUL! There are a lot of things that can generate too low a reading on the low side other than insufficient refrigerant (restriction in orfice tube, dirty evap, etc, etc.) If you charge w/o a high side gauge under these conditions you may go way over on the high side and damage your car and/or you.
Also remember, the longer you run the car in the shop the higher the press will creep. Just like eng temp. There's nothing real exotic here compared to some issues I've seen discussed on this board, but there are some safety issues. One last thing, a high side hose connection blowing apart while you have your head under the hood could cause a massive cardiac arrest for old guys like me. Don't ask me how I know this. As always, JUST MY OPINION, OTHERS MAY DISAGREE.
