low side pressure high
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Junior Member
Joined: Nov 2010
Posts: 4
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From: Charlotte, NC
low side pressure high
New owner of a 98 expy 5.4.
I recently I noticed my a/c compressor was cycling (on panel&floor for some reason, in addition to all other a/c and defrost settings) and read all of the threads which pointed towards low system pressure. However, when I hooked up the r134a booster can, my low side pressure was already in the yellow ~50psi. A/C on full blast.
I'm not sure where to go from here and really can't afford to pay shop rates. Could it be a bad LP switch? Something else I'm missing here? Obviously I'm not worried about my A/C right now, but I need defrost and I don't want to damage the compressor.
Any help is greatly appreciated.
I recently I noticed my a/c compressor was cycling (on panel&floor for some reason, in addition to all other a/c and defrost settings) and read all of the threads which pointed towards low system pressure. However, when I hooked up the r134a booster can, my low side pressure was already in the yellow ~50psi. A/C on full blast.
I'm not sure where to go from here and really can't afford to pay shop rates. Could it be a bad LP switch? Something else I'm missing here? Obviously I'm not worried about my A/C right now, but I need defrost and I don't want to damage the compressor.
Any help is greatly appreciated.
Senior Member
Joined: Oct 2002
Posts: 7,295
Likes: 125
From: St. Louis (Out in the woods)
It is completely normal for the "low" side to read "high" when the compressor isn't running.
The system should equalize at the static pressure that is normal for the under-hood ambient temperature. For R134a, it's close enough to assume the pressure in PSI is just slightly higher than the temperature in degrees F. Consult a refrigerant PT chart for exact values.
See FAQs at sister site http://www.ford-trucks.com/forums/75...xpedition.html
The system should equalize at the static pressure that is normal for the under-hood ambient temperature. For R134a, it's close enough to assume the pressure in PSI is just slightly higher than the temperature in degrees F. Consult a refrigerant PT chart for exact values.
See FAQs at sister site http://www.ford-trucks.com/forums/75...xpedition.html