96 Suburban AC not working

[87Skier]

So I've had my Suburban for a year now and I figure I should fix my AC even though summer is almost over.

Some background: First, I don't work on AC systems much and don't have a lot of prior experience with them. Second, I don't know when the last time it worked was. Third, the suburban has rear AC (not sure if that changes anything).

When I got it I thought I would check out an electrical issue, so I turned on the AC and jumped the pressure switch on the passenger side of the suburban, the compressor kicked on and clutch engaged properly. I immediately disconnected it to prevent damaging the compressor. Next, I thought it might just be low on R-134a so I used my left over recharge kit on the suburban. When I hooked it up and starting charging my system, the compressor kicks on. As soon as I released the trigger, the compressor would turn off.

I'm not really sure where to go from here. Is my system leaking? Do I have a bad switch?

Thanks

[Kudzupatch]

Have you checked the pressure readings? First impression is you don't have enough pressure/freon in the system. Really need gages to see what you have and how much freon to add.

[87Skier]

I haven't really checked them unless you count the gauges that come on those cheap refill kits. Even then it didn't really register.

Should I look at buying a set of gauges?

[Kudzupatch]

Originally Posted by 87Skier

....... Even then it didn't really register.

Should I look at buying a set of gauges?

Have to assume the gage is at working but it is it not reading your compressor is not going to cut on. I don't know now much but you have have a certain amount of pressure of the compressor to cut on. If you have no or not enough the compressor will not come on.

Got to be careful but you can jumper the switch to see if the compressor works.

[87Skier]

Originally Posted by Kudzupatch

Got to be careful but you can jumper the switch to see if the compressor works.

That's the first thing I checked. If I jump it where it goes into the truck, the compressor kicks on like normal. I did it twice and ran it for no more than a second to hopefully avoid damage.

[Kudzupatch]

My bad, I should have reread the original post. Sounds to me like you just don't have enough (any?) freon in it to trip the switch. But with a gage it is hard to say. Not sure what the pressure it takes to trip the switch is.

Just put a new compressor on mine and I think it took 6-7 cans for get it full and I have rear air too.

[The_KC_Kid]

I am a certified auto a/c tech, 3rd generation family owner auto heating and cooling shop. First, jumping the pressure switch tells u two thing, 1 the compressor clutch is still good, 2 the electrical system ( wires them selfs) are operating properly. The thing they dont tell u on the "a/c pro" advertising is that if ur having to add freon to ur vehicle, that there is a leak SOMEWHERE. When freon leaks out it also lets air in, when there's air in the sytem ur gauge set could show proper levels but u could only have 1lbs or freon and 2lbs of air trapped in the system. U need to take it to shop that has a A/C machine that will pull the system into a vacuum and get rid of any air and moisture in the system.

There are two things ALL 88-98 GM fullsizes are bad about. First thing is the a/c fitting on the line that bolts to the top of the compressor, it uses a rubber ball instead of a shrader valve and the rubber deteriorats over time and leaks. Second thing is the compressor seal itself. The original compressor that came on 95 and up (I belive 95 off the top of my head) use a multi piece comp housing that is pressed together when manufacturer and uses 3 big o-rings to seal the compressor itself. Easiest way to check if comp is leaking is look at and if there is oil residue ontop of the compressor, the o-rings have gone bad and its time for a new compressor.

Hope this helps u out and if have any questions just message me.

[87Skier]

Thanks for the information KC_Kid.

What you are saying makes sense and is what I thought would be the case before I even started. The main reason that I wanted to look into this is to fix any issues before I took it in to have it serviced as they usually charge an arm and a leg to fix things like this.

Would it be worth getting a leak detection kit and checking all the other places there could be a leak? I've heard of other suburbans that have ruined the rear AC lines, but I don't see any physical damage.

[Kudzupatch]

Originally Posted by The_KC_Kid

.......When freon leaks out it also lets air in, when there's air in the sytem ur gauge set could show proper levels but u could only have 1lbs or freon and 2lbs of air trapped in the system. ............

OK, got to ask how air gets in to replace freon? Maybe I am missing something but this statement doesn't make sense.

You are talking about a sealed system under pressure. When it develops a leak, the gases inside escape through the leak to the lower pressure side, the atmosphere. So how does air get inside a pressurized system to replace the freon?? You said the system can show normal pressure but be low of freon. Atmosphere air pressure is lower than the system so how does it overcome the higher system pressure and enter the lines?

[The_KC_Kid]

There are two "sides" to the a/c system, a high side (pressure) and a low side (suction).when the compressor is on the high side can get upwards of 300+ psi and the low side runs somewhere around 30-40psi when system is filled to spec. When the system has a leak in it the low said can go into a vacuum pulling in outside air in. Go buy a sealer bottle of water, now imagine that inside that bottle there is freon instead of water. Now take a small needle and poke a hole in while leaving the cap on. When the water is done leaking out, what are u left with? A empty bottle of air

[The_KC_Kid]

Originally Posted by Kudzupatch

My bad, I should have reread the original post. Sounds to me like you just don't have enough (any?) freon in it to trip the switch. But with a gage it is hard to say. Not sure what the pressure it takes to trip the switch is.

Just put a new compressor on mine and I think it took 6-7 cans for get it full and I have rear air too.

Thats the incorrect way to do it also, u may get the compressor to come and and blow SOME cool air but it will never be as cold as its suppose to be and ull cause ur compressor to go bad prematurly.

[The_KC_Kid]

Originally Posted by 87Skier

Thanks for the information KC_Kid.

What you are saying makes sense and is what I thought would be the case before I even started. The main reason that I wanted to look into this is to fix any issues before I took it in to have it serviced as they usually charge an arm and a leg to fix things like this.

Would it be worth getting a leak detection kit and checking all the other places there could be a leak? I've heard of other suburbans that have ruined the rear AC lines, but I don't see any physical damage.

Yes, suburbans are notorious for the rear lines leading. Either where the lines hook the the rear evaporator (very back passengers corner) or where the line hangers are that hold the rear lines up. U could by a leak detector kit, a pretty much free way to do it is get a spray bottle, fill it with soapy water, spray the lines down till u find where it makes bubbles.Also spray inside the fitting ontop of the compressor. U can do it without the compressor running but will be much easier to spot a leak if u jump the switch and make the compressor come on. Before u spray it, look over all the lines and see if u find oil residue anywhere.

[Kudzupatch]

Originally Posted by The_KC_Kid

Thats the incorrect way to do it also, u may get the compressor to come and and blow SOME cool air but it will never be as cold as its suppose to be and ull cause ur compressor to go bad prematurly.

You quoted part of something I said but what is the wrong way?? Using a gage?

[The_KC_Kid]

No, i was talking about the 6-7 cans u said u used to get it full and have rear air. What size cans did u use? 12oz,14oz,20oz?

[The_KC_Kid]

Cuz even if u used the smallest cans u can buy, the 12oz, that means u put 5.4 lbs of freon in a system that takes 4 lbs! 14oz cans, would be 6.2 lbs!

[Kudzupatch]

I don't remember what size the cans were but we filled it to till the pressure readings were where the chart(s) say it should be.