AC Pressure check
Thread Starter
Burning Brakes
Joined: Oct 2004
Posts: 898
Likes: 1
From: Pearland Texas
AC Pressure check
OK, I put the gauges on the AC lines. (Thanks to SunCR) I jumped the cycle switch and got the compressor going. Here are the readings. Low side 30 psi,,High side 220 psi at 72* F with 81% humidity. How does that sound ?
Drifting
Joined: Sep 2003
Posts: 1,363
Likes: 7
From: 1994 LT1 Coupe 6-speed with FX3 & 2000 LS1 Vert 6-Speed with F45 Hunterdon County, NJ
Presume jumping the cycle switch was only needed to get the compressor going so you could charge the system...
At what RPMs were your readings taken?
Also, what freon is in your 1990, R12 or R134a?
Did you happen to measure the temperature of the air from the center vent in the car?
btw, here's a link I have saved on info from suncr (page down a few): http://forums.corvetteforum.com/c4-t...-question.html
At what RPMs were your readings taken?
Also, what freon is in your 1990, R12 or R134a?
Did you happen to measure the temperature of the air from the center vent in the car?
btw, here's a link I have saved on info from suncr (page down a few): http://forums.corvetteforum.com/c4-t...-question.html
Last edited by theadmiral94; Mar 29, 2009 at 11:54 PM. Reason: added link
Safety Car
Joined: Jun 2006
Posts: 3,629
Likes: 28
From: FL
Until SunCR checks in I will comment that according to the pressure chart in my 93 book your pressures look fine, this assumes an R12 system. As theadmiral94 asked the only missing part of the equation is the discharge temperature?
Le Mans Master
Joined: Dec 2000
Posts: 7,839
Likes: 22
From: San Diego, Ca
Assuming R12 and that the Main Fan was running (disconnect the switch) and the compressor was churning with an engine speed of 1500 to 2000 rpms, you could live with it and it isn't going to cycle as frequently (with lower ambients), but it might be a tad too much. I like 26 to 28 psi at 70 degrees (but you might not like the cycling you'll get at 60 or lower). I'd do a couple of things: 1. Make sure the Low Pressure Switch is set correctly. Hook you gages back up and with it on Max, disconnect the blower. That should drop the low and it should cycle off at 25 psi. If not, the Low Pressure Switch has an adjustment screw between the terminals. Turn it counterclockwise to lower the threshold; clockwise to raise it. 2. Get your pressures & vent temps again when it's 80, maybe 85 or better - if the vent is still good and the high isn't climbing north of 250 psi, it should be ok - sounds like you did a good job - congrats!
Thread Starter
Burning Brakes
Joined: Oct 2004
Posts: 898
Likes: 1
From: Pearland Texas
Assuming R12 and that the Main Fan was running (disconnect the switch) and the compressor was churning with an engine speed of 1500 to 2000 rpms, you could live with it and it isn't going to cycle as frequently (with lower ambients), but it might be a tad too much. I like 26 to 28 psi at 70 degrees (but you might not like the cycling you'll get at 60 or lower). I'd do a couple of things: 1. Make sure the Low Pressure Switch is set correctly. Hook you gages back up and with it on Max, disconnect the blower. That should drop the low and it should cycle off at 25 psi. If not, the Low Pressure Switch has an adjustment screw between the terminals. Turn it counterclockwise to lower the threshold; clockwise to raise it. 2. Get your pressures & vent temps again when it's 80, maybe 85 or better - if the vent is still good and the high isn't climbing north of 250 psi, it should be ok - sounds like you did a good job - congrats!
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