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Puzzled by pressures?

JohnnyWS on Tue May 26, 2009 5:28 PM User is offline

Year: 2003
Make: Nissan
Model: Frontier
Engine Size: 2.4
Refrigerant Type: R134a
Ambient Temp: 85
Pressure Low: 5 psi
Pressure High: 5 psi
Country of Origin: United States

I realize the pressures look weird in the profile, but that's what I was getting on my father-in-law's truck. There is refrigerant in the system, and my gauge set reads fine on my 2002 Xterra (nearly identical systems), but on his truck, the reading is about 5 psi on both the high and low side with the system running. The A/C clutch engages, but won't disengage until the engine is shut off. To double check the reading I hooked one of those "low-side-only-blue-green-yellow-red" gauges to the low side port and read about 25 psi with the system off. Clearly I must be doing something wrong with the gauges, but I got normal readings on the Xterra following the same procedure. Also, there must be enough refrigerant in the truck's system to keep the low pressure cutoff switch happy. Does this sound like a failed compressor, or some problem with the expansion valve? Any idea what I'm doing wrong with the gauge set? Thanks.

Chick on Tue May 26, 2009 7:57 PM User is offlineView users profile

Have the system evacuated, a deep vacuum pulled and the correct charge into the vacuum. If all you have is 25psi at 80 degrees ambient the system is empty.. You should find and fix the leak first of course, but if you can't find it, add some UV dye to the system when you recharge it..Hope this helps..

Email: Chick


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