Low side should be about 30 psi at idle speed, high side 120 to 180 psi depending on ambient temp. higher temp, = higher pressure, as you increase engine rpm to say 1000 low side should drop to 10 to 15 psi & high side should increase about 30 psi. If high side goes over 280- 300psi you have contamination (air) in system or over charged with refrigerant. you will need to recover freon, evacuate & recharge system with proper amount of refrigerant. If the low side drops below 0psi or into vacuum then the refrigerant level is low, you will have to check for leaks , repair leaks & refill refrigerant.
Hope this helps
Paul T
The pressures will vary with temperature and humidity but a good ball park figure would be 25-45 psi for the low side and 150-220 for the high side.
SOURCE: 1995 pontiac grand am: AC
You take your car to the nearest licensed automotive A/C shop and have them evacuate the system and recharge.
I'm saying this because once you have opened the system, you have let moisture into it. Even a small amount of moisture will damage your A/C system, and needs to be removed. Also, they will know just how much refrigerant to put into the system once it is moisture free.
SOURCE: Adding freon to air conditioner
If your system takes R-134 then the fittings for the high and low pressure are different sizes. You should only be able to fit the connector on the low pressure side.
SOURCE: Need location of Low and High pressure ports for Air Conditioner
it will be in the line itself, the larger line, it will look like an inflater for a tire,should have a black plastic cap on it
SOURCE: Adding freon to air conditioner
from the compressor there is two lines coming
from the back side, follow the line that goes
in to the front condenser thats your low side.
G
SOURCE: location of low side pressure value for a/c
low pressure line from the AC compressor, that is the larger line of the two lines comming from the AC compressor
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