ahardb0dy Posted July 29, 2012 Share Posted July 29, 2012 My 90 sentra the AC has not worked for a while now, probably need another new compressor, I picked up a can of freon with the gauge and hose the other day for my step daughters car and I wanted to see what the gauge said when I hooked it up to my sentra, low side of course. I start the car, AC on, compressor clutch is engaged, with the gauge connected to the low side port I get no reading at all, needle doesn't even move. Today I tried again with the engine off and the gauge gives a reading, I start the car and check it again, no reading. Anyone have any idea why it is doing this??? Thanks Also checked the pressure in the pathfinder, was slightly low so I gave it a quick hit of freon, the AC in the PF always works just takes a while to get cold, I figure this is part because it takes a while to cool the inside air and partly cause my windows are not tinted, but after adding a very small amount of freon it actually got cooler quicker and feels like the air coming out of the vents is colder too. Link to comment Share on other sites More sharing options...
nztim Posted July 29, 2012 Share Posted July 29, 2012 In those 90's sentras and pulsars (my old one included) the relays where pretty common to pack up on the unit. is there current to the compressor? Link to comment Share on other sites More sharing options...
ahardb0dy Posted July 29, 2012 Author Share Posted July 29, 2012 The compressor clutch is engaged, I've had bad luck with the reman compressors the one in the car now is like the 4th one I put in there, they usually last a year than take a crap. The one in the car now was a cheapy unit I bought off e-bay and it didn't even last 4 months. The rest of the system is good. When we replaced the compressor last time I had my guy flush out everything, I was there when he did it, watching and helping him. Just have no idea why the gauge shows no reading when the engine is running and the AC is on but when the engine is off it does??? Link to comment Share on other sites More sharing options...
andreus009 Posted July 31, 2012 Share Posted July 31, 2012 Well, I'm not AC guy but from what I recall from watching the gauge while the compressor cycled the needle would go down while the compressor was running and then would go up when the compressor cycled off. Did you try running the engine and turning the AC off? My present guess (not being an AC guy) is that the system is real low on freon so that when compressor kicks on, it just pulls the pressure down to an unreadable level. It is connected to the low side which I'm assuming would be the suction side of the compressor so what I'm saying kinda makes sense. (At least to me anyway). Link to comment Share on other sites More sharing options...
ahardb0dy Posted August 2, 2012 Author Share Posted August 2, 2012 I need to get a set of gauges before I try to diagnosis any problems, thanks Link to comment Share on other sites More sharing options...
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