I have a 99 C3500 CCLB with the 5.7 and NV4500. About 2 months ago I started having the A/C compressor cycle on and off repeatedly. I dont drive the truck often since its mostly a tow rig and I ride motorcycle to work. So i ignored it for a month. It was my understanding that this can be caused by low pressure. But when I hooked a cheap ass gauge up to the low pressure side, it was showing around 100psi. So I bled some pressure (i know im a horrible person...the ozone layer hates me) well once I did that, the ac compressor stopped cycling all together. Tonight I borrowed a nice manifold gauge from my dad ( should have done this in the first place) the low pressure side showed around 50 psi and the high side around 50 psi as well. I hooked a can up and got the low side to about 90 psi ( i am well aware how high that is) and the high side to about 100 psi. Compressor still will not kick on. I checked fuses and relays with no luck. I am stuck at this point. Any ideas?
Hi-someone said on one of the threads,that it's hard to refill with cans,as at some point pressure from them can't overcome the pressure from the system-or something along these lines. Idl cause I always took mine to the garage to have it refilled-I bought mine with non working AC. First thing we've done(my friend in a friendly garage) was refilling the system and adding pag with dye. I suggest to do the same(preferably in a friendly garage,which will take refrigerant back when/if you find the leak-as from the symptoms you may have a leak). It may be small, but enough to disable the system. Also bridge the pressure system to check if it engages clutch on compressor-tho by what I read so far I don't think sensor is a problem,as it was engaging and gradualy stopped. I can't remember exactly how it's done-you'll find it on youtube.
Get yourself a black light torch from ebay or wherever.Once you have dye in the system-run it and in the dark shine it with uv light-and search for the leak. Go along the piping-especially on joints,condenser(corners and where the pipes go in),everywhere. If you won't find any then this is out of equation and you canfocus on electrical/mechanicalside of things. Maybe compressor seized?
Obe of the things you can do before refill is to find the orifice tube( mine's near passenger inner fender,near Y-pipe,where it joins with another pipe-I have 99 Tahoe)and check it for metal shreds/bits-it will tell you if something has gone wrong with the compressor.