General Maintenance & Repairs - no a/c, but high pressure??
12-10-2007, 10:40 AM
i tried a quick search but didnt find much on the subject. i just bought a 2000 z28 and thought it had a nice cold a/c. well now that its 85, yes 85 degrees i have found it just blows warm air. now, i had a can of quick refill refrigerant and was going to use that, but the pressure gauge on the tube from the can was in the 75# area, and the can recommended that you not refill it because there is a problem. Now i was not born yesterday and wont take a rattle cans advice, but i have no knowledge of the inner workings of the a/c system. The fans work well, but are loud in high mode and dont know if i should just take it in for a drain and recharge. I kinda am ruling out a leak since that would cause the opposite reaction. Any ideas?
12-10-2007, 12:45 PM
I'd check the vacuum actuation, see if there is a leak or
blockage to the diverters under the dash. Does the A/C
clutch engage and run while it's blowing warm? Or fast
A set of $39 Harbor Freight manifold gauges would tell
you a lot more about the system than the low side
alone. You want to know if the high side is getting
pumped or if the thing is just sitting at baseline
pressure. As I recall, 75# is kind of high for low side
pressure when running.
12-10-2007, 12:49 PM
Sounds like the compressor isn't coming on, so you're reading static pressure. 70 psi with it off at about 75 degees should be enough to keep it from tripping off for low pressure and check the charge. Low side pressure with the compressor running should be 40-44 psi at 76-85 degrees according to my helms.
12-10-2007, 08:24 PM
also see if you have any heavy frost built up around any of your lines, especially around your accumulator, this'll tell ya that you might have a clog in your system. you can also feel in front of your condenser for any sharp changes in temperature( it should be a gradual change) this can also point out a clog--im no expert on A/C this is just some of the basic stuff i learned recently
12-10-2007, 10:18 PM
If the fans are on high with a command for a/c but the compressor is not coming on chances are you need a tech 2 too look at the high side pressure sensor and see what it is reading. Usually the sensor will fail and tell the pcm it has 300 LBS plus of pressure. Default is a/c clutch off and command the fans to high speed.
RE AND CHERYL
12-11-2007, 11:31 PM
The system also won't come on if the low side press is too high. Try letting a little pressure out on the low side. If the system was overcharged a bit when the outside temp was colder the press would be a little lower and the system work, but the press be too high to come on when temps get warmer.
12-12-2007, 12:23 AM
i dont see any frost anywhere, and when you talk about the fans coming on when i turn the system on, are you referring to the main fans that will turn on no matter if the tstat has opened or not?
12-12-2007, 06:40 AM
Regardless of the engine ECT if the A/c pressure switch is having issues on a command for a/c, the compressor will be commanded off and the main engine fans will go to high speed to protect itself from high pressures. In this case it is false probably bc the switch on the liquid line by the evaporator is bad. If that is the problem then when it is replaced the fans will go back to normal and a/c compressor clutch operation will resume as normal and yo will have cold air then Dont let any refrigerant out. 75 on the low side with the compressor off is normal it is usually between there and 100 or so depending on the outside ambient.
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