2001 2500 HD blows hot air while idoling

I have a friend who is a mechanic, sort of, and he has a/c manifold gauges, i do residentail work, so i figured i would see what the gauges read. When I put them on, the liquid side would rise up to retard causing the compressor to go out on overload then when it would drop, come out of it then go right back up as fast as it came down. My thoughts were maybe the metering device between the ports? But it only does it while idoling, when i get out on the highway and rev it up it seems to work fine. Any ideas?

I have a friend who is a mechanic, sort of, and he has a/c manifold gauges, i do residentail work, so i figured i would see what the gauges read. When I put them on, the liquid side would rise up to retard causing the compressor to go out on overload then when it would drop, come out of it then go right back up as fast as it came down. My thoughts were maybe the metering device between the ports? But it only does it while idoling, when i get out on the highway and rev it up it seems to work fine. Any ideas?

your high side pressures will fluctuate as the clutch kicks in and out.

what are your psi's when the compressor is running with the clutch engaged??? if it's fluctuating often, (every 5-15 seconds or so) it sounds as if the charge is low....

i believe it should be 32-34 low psi and 180-200 high psi. (high side) not positive about that.

the warm air is due to lack of refridgerant and the condensor is hot. at higher rpms.... it's circulating and works much better.......

if its cold when driving and hot at idle you might want to check the clutch fan if it has one, kinda sounds like not enough air flow across condensor, will cause excessive high side pressure, quik was to check is use a house fan and put it against front of ttruck blowing into radiator and see if a/c getts colder

Did you by any chance change out your crank pulley? I put an underspeed unit on my truck and the A/C was warm at idle and fine when moving. There wasn't enough RPM's to make the compressor happy.

Thanks alot all.

Thanks alot all.


or check this out....

http://www.automotiveforums.com/vbulletin/showthread.php?t=244030

2nd entry..... i was unaware of this. might be related to your problem.