Help with A/C problem

[ledroyjr]

2000 GMC Sierra 2500 4X4 6.0L air stopped working, changed out relay did not change situation, learned there was a cabin air filter changed it out was very dirty. The A/C started working and was cooling fairly well, then it started to blow hot air when you got in a slow down situation on the road about two weeks later. Replaced cabin air filter again about two months after the first change, was dirty but not as bad as the first change out but did not change the situation. I got a pro air charge unit and proceeded with their directions, showed that the unit was filled, I closed the doors to the rig so it would cycle and watched the gauge and it showed the meter on the a/c pro fluctuate between the white area and red area on the meter. It says on the a/c pro meter see tech if reading in the red. So if anyone can help me resolve where I am at on this I would appreciate the help. Thanks in advance. ledroyjr

[chem_man]

Well, the first thing I would recommend you get a set of real AC gauges so you can look at both the high and low side pressures at the same time.  The can with the gauge that give you colors for the low side pressure ranges is in my humble opinion, a complete waste as it does not provide any usable information when it comes to diagnosing what is or is not going on with your AC system.

 

Also, we would need to know if your compressor is cycling (engaging/disengaging) say every 30 seconds, 2 minutes, etc.  How do the AC lines look - is one completely frosted over, are both dry, is one wet and cold and the other dry and warm, etc.

 

 

[ledroyjr]

I will look at that and try to determine for cycling and line condition.

Thanks for now

Ledroyjr