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Refrigerant pressure

1954 Views 9 Replies 6 Participants Last post by  egheorghe
I checked the refrigerant pressure the other day and it shows 100psi (red on the gauge that comes with the refrigerant can) Isn't 100psi too high? Should I take some out?
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What temperature was it when you checked it? and was the engine running prior to you checking it?

If the car was sitting for a day or so and you check the pressure static (compressor not on, engine not running) It should be roughly 10psi higher than what the air temperature was when you checked it (This method only works in the summer, mid 70's to 100 degree heat). If the engine was running prior to you checking it, it's going to be hot and read a higher psi.

Are you getting any codes referring to the A/C system?
Was the compressor running when you tested it? If not you are reading the static pressure of the system and that won't tell you anything.
The temperature outside was 70-75. The engine was not running, but I had used the car like 30 min prior. I don't get any codes related to AC system.
I guess I'm not getting the right pressure because I should check with the engine running and compressor on?
Thank you for the fast response.
100 static psi is high. You really need to check both the high and low side pressures with a good set of gauges. Those gauges on the cans are just feel good stuff and are rather useless.
Static pressure on a hot soak is not any way to check an a/c system.
Are you having a problem with the a/c?
Why do you care what the pressure is? The only way to check the a/c system is running on max cold with high blower and a proper gage set to read both high and low side pressures.
Anything short of that is guessing but without knowing why you want to check it we are all pretty much in the dark anyway.
There is nothing wrong with the AC, it's just that I haven't used the car like in a week (I've been laid off from my job - now I'm a free man :)) and I am planing to have a 1000 mi trip. The other day the car stalled on me and I started to check the major things to make sure my trip will be safe and comfortable. I guess I need to run a jug of Techron for the fuel system (i haven't done it in a long time) I checked the fuel pressure too and it looks ok - 45 psi and 50 psi when I unplugged the vacuum hose from the FPR. I didn't get any codes therefore I assume it was just some ugly stuff from the bottom of the gas tank.

Today I checked the refrigerant pressure with the engine on and the AC at max - everything it's ok there too. I didn't know how I was supposed to check it to get the correct readings.
Thank you for all the replies, you guys are cool and this is the greatest forum.
If you think there is something else I should check before hitting the road, I'm open to any suggestions.

BTW, I checked the fuel pressure at the connection right before the first injector (driver side). Is that the right way of measuring the pressure?
There is another connection close to the FPR with a green cap. What is that for?
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Fuel rail bleeder fitting. Pressure test port.

The only way to test refrigerant/system pressures is as ewill3rd described - with a proper gauge set and specific operating conditions. Static pressures are absolutely meaningless.

If the engine stalled unexpectedly, have you looked at your (possible) Diagnostic Trouble Codes ??? That operation alone will drive you paranoid right before a long trip.

Check the pressure on the dumb spare tire donut - no one ever does until it's too late. Throw a quart of your favorite engine oil in the trunk. Set all 4 tires to 33 psi COLD and don't ever bleed them hot. Torque all the lug nuts sequentially to 100 ft/lb. Put new batteries in your flashlight. Keep a written fuel mileage log, and don't reset the average fuel mileage display until after the entire trip - you have no idea of true mileage if you reset it every tank.........
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BTW, I checked the fuel pressure at the connection right before the first injector (driver side). Is that the right way of measuring the pressure?
That is the ONLY way to check the pressure.
There is another connection close to the FPR with a green cap. What is that for?
I believe that is the EVAP system test port. I'm not exactly sure how it is used though.
Thanks Submariner and Ranger!
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