A/C pressure when off.
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More Turbo
Joined: Dec 2011
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A/C pressure when off.
According to the service manual the pressure should be 42+ PSI when the truck has not been run for awhile, mine checks 52 PSI so I thought the refrigerant system has no leaks. Anyway, the A/C doesn't cool at all. Since I have the extended warranty I took it to the dealer where they said the evaporator needs replaced. I wonder if they are correct or are they padding the bill? I'm not looking forward to the entire dash being torn out needlessly. Your thoughts?
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More Turbo
Joined: Dec 2011
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L1 CHECK THE A/C SYSTEM PRESSURE
. Ignition OFF
. With the R-134a manifold gauge set connected, check the A/C system pressure.
. Is the A/C system pressure above 290 kPa (42 psi)?
Laughing Gas
Joined: Jul 2020
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If you could post that page it would be helpful. But I believe all that is testing for is to verify the pressure switches are satisfied. Not for leak testing as such. And definitely not a positive test if the refrigerant is up to snuff.
Laughing Gas
Joined: Feb 2007
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R134a Static pressure chart
Static pressure is the pressure with the system at rest (compressor off for at least 30-mins). Attach to the hoses and gauge set to the high and low side ports of your AC system.
1. With the engine OFF for at least 30 minutes, read the low and high-pressure gauges. They should be the same because the high and low side pressure equalize once the compressor shuts off. It takes a while to equalize, that’s why you must wait 30-mins to check static pressure
2. Measure ambient air temperature at the vehicle and under the hood WITH A THERMOMETER (do not use weather service temperatures). The static pressure correlates to the temperature of the AC components under the hood, not outside in front of the vehicle.
3. Compare the pressure readings to the pressure-temperature chart below
1. With the engine OFF for at least 30 minutes, read the low and high-pressure gauges. They should be the same because the high and low side pressure equalize once the compressor shuts off. It takes a while to equalize, that’s why you must wait 30-mins to check static pressure
2. Measure ambient air temperature at the vehicle and under the hood WITH A THERMOMETER (do not use weather service temperatures). The static pressure correlates to the temperature of the AC components under the hood, not outside in front of the vehicle.
3. Compare the pressure readings to the pressure-temperature chart below
Hotshot
Joined: Jul 2013
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According to the service manual the pressure should be 42+ PSI when the truck has not been run for awhile, mine checks 52 PSI so I thought the refrigerant system has no leaks. Anyway, the A/C doesn't cool at all. Since I have the extended warranty I took it to the dealer where they said the evaporator needs replaced. I wonder if they are correct or are they padding the bill? I'm not looking forward to the entire dash being torn out needlessly. Your thoughts?
the psi when cold should be no lower than ambient temp. If the psi is lower than ambient temp, it’s too low on Freon to troubleshoot.
Once you satisfy the above, when you start the vehicle, the suction side should drop and the pressure side should increase…if it does not…your clutch is not engaging and there are various reasons for this.
if the second item above is met…then you can adjust the suction side to match your target interior vent temp. If you want the vent temp to be 40 degrees, you may need to add or lower Freon to meet that goal.
there are charts that scale ambient temp vs psi to help you reach your desired vent temp.
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More Turbo
Joined: Dec 2011
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the psi when cold should be no lower than ambient temp. If the psi is lower than ambient temp, it’s too low on Freon to troubleshoot.
Once you satisfy the above, when you start the vehicle, the suction side should drop and the pressure side should increase…if it does not…your clutch is not engaging and there are various reasons for this.
if the second item above is met…then you can adjust the suction side to match your target interior vent temp. If you want the vent temp to be 40 degrees, you may need to add or lower Freon to meet that goal.
there are charts that scale ambient temp vs psi to help you reach your desired vent temp.
Once you satisfy the above, when you start the vehicle, the suction side should drop and the pressure side should increase…if it does not…your clutch is not engaging and there are various reasons for this.
if the second item above is met…then you can adjust the suction side to match your target interior vent temp. If you want the vent temp to be 40 degrees, you may need to add or lower Freon to meet that goal.
there are charts that scale ambient temp vs psi to help you reach your desired vent temp.
Understood. The service manual should have included the temperature in the pinpoint test. The whole idea of the simple test was to determine if there is a usable quantity of refrigerant before wasting time proceeding with electrical tests. In my case, it appears that there was ample refrigerant so my concern is that the evaporator may not be faulty. Perhaps they picked up a leak with a sniffer, I will check it today with my cheap Harbor Freight unit. The truck is scheduled for the autopsy on Tuesday. Watch a YouTube video to see why I am concerned with the work required to replace the evaporator.
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