this 99 a/c is blowing a warm to cooler and never ice cold. I do have my low pressure Schrader leaking alittle bit but once its coupled with guages its sealed off. so I put u/v dye and cant find a leak yet. I hooked up gauges. my reading with car off is 100psi on each side.with the car running and a/c off the low is 87 psi and high is 115psi
when its running with a/c on its 20 psi low and 150 psi high.
the second it looks like its down to 18psi low and 135 high


facts of whats going on .....
1. the compressor constantly runs and does not cycle not sure if its suppose to.
2. the low pressure line does not get cold .
3. the evaporator drips plenty of water normally.
4. high pressure gauge seems to be sold but low pressure guage seems to float alittle

 

but then reaches 20-21 psi and 150 and running for about 10 mintutes

 

What were air temps when the pressures were taken? Normally would expect cooling w/ that much differential unless it's really hot/humid (Houston for instance). Low side is low which suggests low charge since thermostat did not detect low evap temp and disable compressor.

Measuring pressures should be in the shade, AC on, doors/windows closed, Max Fan, Recirculate, and rpm at 1500-2000. Under these conditions high pressure in psi should get to ~ 2.5*ambient air temp degF (100F~250 psi). Cooldown should be 30-40 F (humidity dependent). Measure air temp on floorboard on pax side under glove box and air temp exiting center outlets.

If you're far below the above conditions (low high side, low low side), then charge is too low for cooling.

Have you inspected all connections, condensor face, and ac clutch rotation plane for evidence of oil/dirt accumulation? If everthing is clean, then a slow evaporator leak may be the problem, but suggest re-topping refrigerant to get good cooling (2.5*air temp degF on high side). If cooling is quickly lost, then evap leak is likely. Only way to confirm is with a refrigerant sniffer at the condensate drain (might find a dye indication there also).

good luck

 

it was basically done in the shade at idle speeds.air temps low 80's. condensor is clean but compressor has like oil on it from the engine but only on some of the body areas and def not the head.

 

Suggest repeating test at fast idle as described.


If pressures are normal, cooling should result (check LP fitting right at firewall again).


If LP fitting is not cold, no/low cooling is indicated, and low pressure on LP gauge means low refrigerant charge.


If it's been a long time since refrigerant was last charged, the leak may be very small and tolerable. I've seen evaporators leak at evap/expansion valve connections where brass and aluminum are mated. Fixing requires discharging and removal of evaporator box.


good luck

 

Those low numbers seem too low,,,,Have you tried putting any Freon in at all? The compressor should cycle as well,,if all is ok. Keep us posted on your results.

 

well i pulled the gauges off and then the high and low pressure both were leaking lol so i tried to pull it close but didnt work. so it all drained out over night. i replaced both valves. im going thinking of replacing the drier with a tough one brand but original one still could be good enough???. then i i will do the vacuum but i wish i had a new expansion valve because its not the easier for me to be recovering and recharging. so why would the compressor constantly be running and not cycling ???

 

If Schrader valves remain in place, then atmosphere can only enter when you remove/reinstall new valve. Greater exposure would occur for a replacement receiver/drier.


Compressor will run constantly when charge is low since no cooling to cause thermostat to open compressor. Low side pressure never gets low enough to cause cycling due to low pressure cutoff switch.


good luck