AC Trouble
 

Need Help not sure just by looking which is the service port is on the low side of the air conditioning. I have a 1999 5.3L. I have a prety good idea where it is I think its the second port on the steel line, looks like there is an orifice tube beween the two ports.Some pics would be great pointing out where this is located at

Re: AC Trouble
 

The low side connection would be the bigger of the two. It would be after the oriface. Sorry, I don't have any pics. This is just how it should be. The high side connection should be right off the compressor before the condenser. They are two different sizes. If you are going to use one of those quick charge or refil kits, it will only fit on one line on one connection. Oh yea, It might have a blue cap on it and the high side might be red.

Re: AC Trouble
 

Well I found the right port tried to put freon in found it to be fully charged still have warm air comming out, compresser is engageing and disengageing. air commimng out is in the 60's. Not sure what to do next seem Im not getting good cirulation.

Re: AC Trouble
 

Some of these trucks came with cabin air filters. They can become really clogged, because most people don't know they have them. You may check that. I believe it is under the glove box. My cousin's 02 2500 has one, but my 03 Sierra doesn't. Just something you may check out.

Re: AC Trouble
 

You can't check the charge properly until the compressor will stay on constantly. The cycling on and off is a sign of a low charge. When the compressor is off, the refrigerant will equalize across both sides of the system. So with the compressor off, you will see about 55-75 psi on both ports, then with it running, the high side will be much higher than the low, usually 100psi differance. It still sounds as if the system is undercharged. How did you check the pressure? Do you have guages or are you using the colored charges guage that comes with the refril bottles?