AC Pressure Too High? What's Causing it?


FrankGant
08-02-2005, 07:47 PM
'95 Cavalier 4cyl. A/C has worked without issue the last 2 years. Has a rebuilt compressor purchased 2 years ago. Wife says it started to cool less and less over a couple of days. Car running you turn the AC on and the compressor clutch kicks in. Check the pressure on the (large tube side) and it reads about 150 psi. Same reading with AC on or off with car running as well as when car and AC are off.

If this pressure is normal, what else could be going on here? Thanks.

- Frank Gant

mike2004tct
08-02-2005, 09:42 PM
'95 Cavalier 4cyl. A/C has worked without issue the last 2 years. Has a rebuilt compressor purchased 2 years ago. Wife says it started to cool less and less over a couple of days. Car running you turn the AC on and the compressor clutch kicks in. Check the pressure on the (large tube side) and it reads about 150 psi. Same reading with AC on or off with car running as well as when car and AC are off.

If this pressure is normal, what else could be going on here? Thanks.

- Frank Gant

Probably just running low on refrigerant. Is it an R134A or R12 system?

If R134A, check the pressure on the low side end (Black or blue cap on the line close to the evaporator , the line runs towards the radiator to the condenser), The AC should be on Max with the fan on high for at least 3 minutes, and you should have an optimal reading of 45psi. If it's higher than 45, add 12 oz. of refrigerant. If it's lower than 35psi, you may want to use a leak detector kit to find a leak.

FrankGant
08-03-2005, 12:31 PM
Probably just running low on refrigerant. Is it an R134A or R12 system?

If R134A, check the pressure on the low side end (Black or blue cap on the line close to the evaporator , the line runs towards the radiator to the condenser), The AC should be on Max with the fan on high for at least 3 minutes, and you should have an optimal reading of 45psi. If it's higher than 45, add 12 oz. of refrigerant. If it's lower than 35psi, you may want to use a leak detector kit to find a leak.

The reading of 150 psi is coming from the low side (large tubed) near the dryer and firewall. It's why I as so curious about why it might be that high. Do you still think this is caused by low 134A? If it is low there must be a leak somewhere. Past experiance tells me it's probably the compressor leaking inside again. This would be the same problem we had 2 years ago that prompted us to replace the compressor. I'll put some die in and see if it finds it's way out in the visible areas. Normally though if a system is low the compressor clutch doesn't kick in, but this one still does. But I guess the cheapest and first place to start would be to try and charge it and put some die in and see what happens.

Your thoughts?

mike2004tct
08-03-2005, 12:41 PM
I just recently replaced the compressor on my daughter's Sunfire (The compressor came from a Cavalier), and I had similar readings to what you have before I evacuated the system and added oil and refrigerant.

If you are getting any cold air at all (less and less from your original quote), there's a possibility of air in the system causing the high readings. If you have a 12oz. can of refrigerant, load it in and see what happens. The most you'lll be out is about $10.00, plus, if you add it and the AC continues to degrade, you know you have a leak. you can buy the leak detection kits at most chain parts stores, all you need is an ultraviolet light (black bulb at Spencer's Gift stores does the trick) to check for the dye at all AC fittings.
Good luck
Mike

FrankGant
08-03-2005, 10:02 PM
I just recently replaced the compressor on my daughter's Sunfire (The compressor came from a Cavalier), and I had similar readings to what you have before I evacuated the system and added oil and refrigerant.

If you are getting any cold air at all (less and less from your original quote), there's a possibility of air in the system causing the high readings. If you have a 12oz. can of refrigerant, load it in and see what happens. The most you'lll be out is about $10.00, plus, if you add it and the AC continues to degrade, you know you have a leak. you can buy the leak detection kits at most chain parts stores, all you need is an ultraviolet light (black bulb at Spencer's Gift stores does the trick) to check for the dye at all AC fittings.
Good luck
Mike

Mike,
I purchased a can of 134A and some leak dye. However the system isn't pulling the 134A from the can. Normally when putting it in the can gets cold which is a sure indicator to me it's going in. However it doesn't change temp and the can doesn't get any lighter. I tried it with the can right side up and upside down. Neither way worked. The AC was on and at full blast with the car running of course. Do I have a clog somewhere or is the clutch really not working even though it is spinning. I know the compressor is getting power. The pully spins and then when I turn the AC on the center (clutch section) kicks in. Maybe it's just not working internally and so nothing is circulating?

- Frank

mike2004tct
08-04-2005, 07:46 AM
Mike,
I purchased a can of 134A and some leak dye. However the system isn't pulling the 134A from the can. Normally when putting it in the can gets cold which is a sure indicator to me it's going in. However it doesn't change temp and the can doesn't get any lighter. I tried it with the can right side up and upside down. Neither way worked. The AC was on and at full blast with the car running of course. Do I have a clog somewhere or is the clutch really not working even though it is spinning. I know the compressor is getting power. The pully spins and then when I turn the AC on the center (clutch section) kicks in. Maybe it's just not working internally and so nothing is circulating?

- Frank
I had the same problem initially, shaking the can and holding it upside down while attached to the filler fitting helped.(sounds like you tried this to no avail)

Usually when bad, the center section of the compressor won't spin.

Try this, take a small screw driver and press down on the ball in the valve where you're attaching the refrigerant hose. Press lightly ,only letting the gas out for about a second-don't let it all out- just a little of it. When you go to attach the R134A, shake it up good , then attach it to the tube, put the AC on max with the fan/blower on and engine running (as you did above), then turn the can upside down and shake the can as it's attached to the tube.
If it still won't install, you might have a major blockage beyond my experience.

CDJr
08-04-2005, 08:05 AM
Frank, I hate to be the purveyor of bad news but...if it is kicking on and youre pressure is staying at 150, then the compressor has gone bad again. The reason its staying the same is because the compressor isnt pumping at all. Couldve been caused by a number of things, but it may still be under warranty. It could possibly just be the clutch, but normally when they go bad, theyll make much noise. Lemme know what ya find out.

TONYS-GT
05-08-2006, 01:13 AM
To get the Refridgerant out of the can (shaking it or holding it upside down wont help) Just wrap a warm wet towel around the can.It will force it out of the can,,,,but with 150 psi in your system ,,,setting the can on fire wont even do it.The max pressure should be about 80psi.

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