A/C low pressure 25 high pressure 75, belt squealing
#1
05-27-2011, 03:41 PM
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A/C low pressure 25 high pressure 75, belt squealing
I have a 98 dodge durango. I am very frustrated. It has been 93* here and I can't get my ac to work. I have replaced the dryer, compressor, and metering block, and the belt. I vacced the system down to 25 in/mercury for about an hour. I go to put a charge on it and everything appears to be fine. the compressor kicks on and off while taking freon until it hits 25lbs. on the low side and 75 on the high side, that is when my belt starts squealing. I can't figure out what is going on. HELP!!!!!.
#2
05-27-2011, 10:42 PM
Record Breaker
Is the belt squealing at the compressor (as in the compressor pulley squealing), or is the belt in general squealing as if it is worn down. I must ask this because now with the refrigerant in the system, it is causing the clutch to be under some pressure and add resistance at the pulley, thus causing some tension on your belt. I'd bust out the stethoscope and pinpoint where exactly it is squealing from because you're likely to find it's squealing from a worn tensioner pulley or something.
#3
05-27-2011, 10:43 PM
THE ULTI-MOD
For vehicles currently running with freon R-134a only
Outside-----low side-------High side------Center vent temp
60 F -----28-38 psi----130-190 psi ----44-46 F
70 F ------30-40 psi ---190-220 psi ----44-48 F
80 F ------30-40 psi ---190-220 psi ----43-48 F
90 F ------35-40 psi ---190-225 psi ----44-50 F
100 F -----40-50 psi ---200-250 psi ----52-60 F
110 F -----50-60 psi ---250-300 psi ----68-74 F
120 F -----55-65 psi ---320-350 psi ----70-75 F
_
You can also use this good rule of thumb with R134a, run fan on High with all windows open and engine at 1500 rpm. High side pressure in PSI should be about 2.2 to 2.5 times outside air temperature in degrees F. Example if it's 90 degrees F, high side should be no higher than 225PSI
Outside-----low side-------High side------Center vent temp
60 F -----28-38 psi----130-190 psi ----44-46 F
70 F ------30-40 psi ---190-220 psi ----44-48 F
80 F ------30-40 psi ---190-220 psi ----43-48 F
90 F ------35-40 psi ---190-225 psi ----44-50 F
100 F -----40-50 psi ---200-250 psi ----52-60 F
110 F -----50-60 psi ---250-300 psi ----68-74 F
120 F -----55-65 psi ---320-350 psi ----70-75 F
_
You can also use this good rule of thumb with R134a, run fan on High with all windows open and engine at 1500 rpm. High side pressure in PSI should be about 2.2 to 2.5 times outside air temperature in degrees F. Example if it's 90 degrees F, high side should be no higher than 225PSI
#4
05-27-2011, 10:59 PM
Hall Of Fame
I think he is meaning the high side being taking measurements on the low side port when the pump is at it's highest psi. Not the actual high side port reading.
That being said, at 90 F you should only have about 40-50 psi when the compressor shuts off, at 75 psi you are too full. The compressor is squealing because the system is over charged!
Sounds like the system is working, but instead you have a blend door issue.
That being said, at 90 F you should only have about 40-50 psi when the compressor shuts off, at 75 psi you are too full. The compressor is squealing because the system is over charged!
Sounds like the system is working, but instead you have a blend door issue.
#5
05-27-2011, 11:56 PM
THE ULTI-MOD
i posted that more for the reference conditions that you should be holding the engine at 1500 rpms while taking the readings. also i have heard that if you spend too much time idling spraying the condenser w/ a hose will help to give you better cooling and hence better functioning of the system without the need for the truck to be moving
#6
05-28-2011, 01:32 AM
Hall Of Fame
#7
05-28-2011, 08:04 AM
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ok first off the outside temp was 70 when charging (working on it in the cool of the day). According to the chart posted I should have 35 on the low side, I only have 25. I should have 190-220 I only have 75. With the system off everything equalizes out reads the same on the high and low side. The belt tensioner is fine it is new also. With the clutch off the belt doesn't squeal. The squeal starts when the clutch turns on. The compressor pulley spins smoothly but being the compressor is new it is tight and difficult to spin over by hand. The compressor is serviced with 8 oz of oil from the manufacturer. I did check and conferm.
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#8
05-28-2011, 06:59 PM
THE ULTI-MOD
something i was once told that while working on the a/c system if the vehicle is not moving the condenser may not work at full efficiency , in order to increase the heat transfer off the condenser spraying it with cold water will help to bring it closer to 100% efficiency since water will absorb alot more heat than the air passing over it ever will.
#9
05-28-2011, 08:32 PM
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something i was once told that while working on the a/c system if the vehicle is not moving the condenser may not work at full efficiency , in order to increase the heat transfer off the condenser spraying it with cold water will help to bring it closer to 100% efficiency since water will absorb alot more heat than the air passing over it ever will.
#10
05-28-2011, 09:08 PM
THE ULTI-MOD
i wasnt sure how long you had been idling and working on it so i just threw it out there, not saying it was your issue, but it was something to consider.
if the belt is slipping one of two things is happening, the compressor pulley is locking up when the clutch engages, or the belt is so worn that its slipping under load, you said you got a new belt already so i would look at the compressor. The only thing the PCM controls is compressor clutch engagement by monitoring pressure values in the system.
if the belt is slipping one of two things is happening, the compressor pulley is locking up when the clutch engages, or the belt is so worn that its slipping under load, you said you got a new belt already so i would look at the compressor. The only thing the PCM controls is compressor clutch engagement by monitoring pressure values in the system.