02 Sierra 2500 A/C not working

[EvergreenNJ]

Bought some 134a A/C pro. Measuring the low port, the reading came back as empty. The compressor belt is in tact and running when the AC is on full blast in the truck. The clutch however was not engaging. So with the AC still on high i added refrigerent into the system until it reached 50psi. The clutch began to spin, turning on and off for about 10 minutes until it completely stopped. Pressure remained in the system. The temperature of the air coming out of the vents never really changed, or at least i couldnt feel a difference. I know air conditioning isnt supposed to be too complicated but ive never really worked with it before. Any help would be greatly appreciated. 

Rich 

[Jglew82]

With no refrigerant in the system, that means there is a leak. You must find the leak and repair this first, or else you are just wasting money and releasing refrigerant into the air. The reason you aren't getting cool air is because due to the leak, you now have moisture in the system, so likely the desiccant in the drier is fully saturated.

 

Step one is to get either a leak sniffer or dye and find where the leak is. Once you identify and repair the leak, replace the orifice tube and drier, vacuum the system for 30-45 minutes at minimum, verify no leaks again with pressure readings, then you can recharge the system. 

[EvergreenNJ]

Thanks for the quick response lew. 

I finally made it to auto zone and rented a couple of tools for the job. 

After hooking the up the manifold gauge, i got a psi reading of 20 from the low port and a very low reading on the high. So over a week it went from 40 psi to 20. After bleeding the system I hooked a vacuum up to the system and after about 45 minutes it lost pressure from the vacuum as well. So definitely a leak like you mentioned ( just wanted to be certain).

So I also bought a leak detector, and universal r-134a dye. Does anyone have any tips of using this and pointers on finding the leak? Also, with the vacuum on the system, the low side only seemed to drop while the high side retained the vacuum, is that normal?