Automotive Air Conditioning Information Forum

I replaced the compressor, evaporator exp valve and the receiver dryer on a 99 Maxima. Refrigerant calls for 23 oz of r134 but with that amount the high side was low at only 100 psi. The ambient temp was 89* f. I had to add about 36 oz of 134 to get the high side up to 225psi The low side was high at 75psi and the pressure would not drop. I did add the same amount of oil that was in the original compressor plus 2 oz into the evaporatot. The specs calls for 8 oz of pag 46.

When the system is off the static pressure shows low -225 max on my gauge and high 75. ??? Does anyone have some insight as to what is going on here?

Static Low 225 psi High 75psi

You can't just add 1.5 times the charge based on a pressure reading.

It sounds like a measurement issue.

Hoses on wrong manifold nipples

Schrader valve not depressed by charging hose

hose check valve issue

225 static in the system would mean the system was at around 140f. Possible, but unlikely if you have 75 psi elsewhere.

IMPOSSIBLE-- your low side guage does not read that high on the scale-- you are interpreting the readings incorrectly....

The low side gauge was maxed out all the way clockwise which on my gauge is 225psi. The gauge set was hooked up correctly and not crossed as suggested. The pressure should equalize but the low side is abnormally high. There is ether restriction via the evaporator /expansion valve or thru the compressor. When I opened and released the high side the low side went down slowly. I know that there is too much r134 in the system as it calls for 23 oz but had to add 36 to get the high side up above 200psi. With 23 oz the high side was at 100psi and low at 40. I am thinking bad compressor?

What I am telling you is that there is no way to generate 225 psi on the low side-- low side gauges read to about 120psi then go through a retard zone to max out at 350 or so -- which can't happen. The amount of refrigerant NEVER affects the STATIC pressure- you could have 4 ounces, 4 lbs or 40 lbs in a tank and they would all read the same pressure...Even air entrapment does not read that high...maybe 140 psi at 80 degf at best..

Thanks for all of the input concerning my problem. The rebuilt compressor that I had installed was bad. I could not get the high side pressure up past 100psi. with 25 oz R134 as required for this vehicle. With the extra 10 oz. added the high side went up to 225 but the low side was hovering at 75 psi. I replaced the clutch on the old compressor and put that back in and everything works fine. Back to sub 50 deg temp in the cabin.