A/C issues

[99 3500 CCLB]

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?

 

[Schurkey]

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?

Stop screwing with it, take it to a professional.

Anyone who bleeds off pressure, and doesn't understand why the low side and the high side have the same pressure when the compressor isn't running should not be dicking with A/C systems.

At best, an on-site mentor would be a great advantage.

 

[99 3500 CCLB]

Stop screwing with it, take it to a professional.

Anyone who bleeds off pressure, and doesn't understand why the low side and the high side have the same pressure when the compressor isn't running should not be dicking with A/C systems.

At best, an on-site mentor would be a great advantage.

Pardon me for not being an expert and trying to learn a thing or two. The best way to learn how something works is to screw around with it. Sometimes you break stuff but you learn best from mistakes. Ill be sure to run anymore questions by you before I ask. I also sincerely hope that you arent an example of how the rest of this community is...

 

[Dariusz Salomon]

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.

 

[PlayingWithTBI]

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

You can charge it with cans, you simply add refrigerant with the engine off until it doesn't take anymore. Then start the engine, turn on the A/C so the compressor will suck down the low side lower than the current pressure in the can. Sometimes you'll need to rev up the engine to suck the last bit left in the can. There will always be some residual in the cans but, usually about the same as the low side when the compressor is running at a higher speed.

A word of caution, while charging the system using manifold gauges, don't open up the high side valve on the gauges!

 

[SuperSpore]

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?

Your expansion valve is bad. You have to replace it and recharge the system.
It's like 40 bucks for the valve.
When your high and low pressure systems won't balance it's usually the expansion valve.
If you take it in, the shop will tell you you need a new compressor.
If you replace the valve, and it's still not balancing then it's possible the compressor has failed, and it may have contaminated your system.
But that's worst case. It's almost always the valve when hi and low are off.

 

[xXxPARAGONxXx]

The best way to learn how something works is to screw around with it. Sometimes you break stuff but you learn best from mistakes.

If one wishes to learn from mistakes, it is best that they are others’ mistakes.

 

[someotherguy]

Your expansion valve is bad. You have to replace it and recharge the system.
It's like 40 bucks for the valve.
When your high and low pressure systems won't balance it's usually the expansion valve.
If you take it in, the shop will tell you you need a new compressor.
If you replace the valve, and it's still not balancing then it's possible the compressor has failed, and it may have contaminated your system.
But that's worst case. It's almost always the valve when hi and low are off.

You'll know pretty quickly if the screen on the orifice is loaded with shrapnel. Also, if it's all black and gunky.. time for a very thorough system flush. A new compressor will be wasted near-instantly otherwise.

Richard