99'CajunFirehawk157

iTrader: (57)

99 GM Fbody ls1 5.7, original a/c compressor seals went out @ 70k miles & 14yrs after leaking for a year or so. This weekend I replaced the compressor, orifice tube, and dryer as well as all of the o-rings/seals after they were lubricated with the appropriate mineral oil per GM specs. All connections on compressor were torqued to factory specs. Pulled a vacuum on the system for over an hour the first time, let it sit almost an hour and the vacuum held perfect. After putting in the correct amount of PAG oil per gm specs, attempted to put the first 12oz can since the system holds 1.5lbs (24oz) totally empty. Since the system was 100% empty of R134a, the pcm apparently kicked in its electronic "low pressure switch" and would not let the compressor engage so as to take in the new R134a. As I understand it, these newer gm cars do not have a normal low pressure switch that can be jumped from one pin to another to engage the compressor long enough to get some R134a in the system to fill it? My first attempt charging the system yielded a super high pressure between 90-120lbs on the low side reading which would suggest that pressure is caused by the compressor not cycling the Freon thur the system, plus it had very lil freon, maybe an once or two max and would not take anymore ? So how do I get R134a into this 100% empty system?

SilverSS07

iTrader: (1)

I don't know if this is the completely correct way but this is what worked for me. Disconnect the battery for a little bit to let the computer reset itself. While the car is shut off charge the system with as much r134 as it will take. Once it won't take anymore start the car up and turn the ac on. It should have enough in it to not disable the ac.

99'CajunFirehawk157

iTrader: (57)

Thanks, I assume you charged via the LOW side port? IF so, I tried charging it w/the engine off and it would only take r134a up to the point where the compressor is and then would not take anymore, maybe an ounce or two. But I will try the battey thing, you may be on to something, hope so...

Thanks.

SilverSS07

iTrader: (1)

Yes charge the low side port. It won't take a lot of r134 but it should be enough to allow the pcm to enable the ac. Once the pcm disables the ac unless you have a scanner or some other way to reset it then the only way I know of is to disconnect the battery. That's how I had to do it on my 95 and it worked fine.

99'CajunFirehawk157

iTrader: (57)

Wow, thanks!! I unhooked the battery for about 15 minutes and Wa-la, the compressor kicked in a few times, no problem. I then burnished the clutch per instructions and it is charged, good to go!