A/C problem

[or2tx2002]

I have a question about our 93 Chevy Suburban's A/C unit. We have never had any A/C problems before, but suddenly today when I got in vehicle the A/C is just blowing hot air. The hot air is out of front and rear vents. My hubby is out of town for the week and I'm on my own until then in the August heat in Texas so any info would be greatly appreciated. I lifted the hood and the belt is still on compressor but the thing (don't know what it is called) that is at front of compressor that should be clicking/cycling off and on isn't moving at all. I can move it manually with my hand if vehicle is off but it won't move on its own like it is suppossed to. What is this part called and is it something that can be purchased at a parts store and replaced at home or does it require freon to be drained and a actual mechanic to do the work? I am just trying to determine if this is something hubby will be able to do once he is back or if I am just wasting time not taking to mechanic if I am going to need to regardless if it isn't something he is able to fix due to freon. What would make this part not cycle/click/spin? I'm sorry for what is probably such a stupid question but I have four kids and it is miserable here without A/C and until hubby gets home we are on our own.
Thanks again,
Tricia

[Ryan685]

The freon pressure is low. It doesn't mean it's empty though. There is a pressure switch in the system that will not allow the compressor to kick on if the freon is low. A shop may or may not charge the system back up if it has a leak. They will want to repair the leak, probably an O-ring somewhere. Worce case for leaks is a compressor seal or worce, an evaporator or condensor. One is inside the dash, the other is in front of the radiator and looks like a radiator. Leaks usually have oil around them from the freon to kind of show you where it's leaking. Leaks are very slow sometimes. Maybe a month or more to get low enough to cause what you are seeing at this time. Your best bet is to ask the neighborhood shadetree mechanic to add a can of freon to get you through the month. He will need to know something about air-conditioning, like if your truck takes 134a freon or R12. Not everyone can buy R12 because they stopped making it, it's a danger to the ozone layer around our plannet. R12 is about $65.00 a can or more depending. 134a is around $10.00 a can. I can't say if '93 has 134a or R12. You can't mix the two because of different fittings for the two freons. If you take it too a shop and your truck has R12. R12 has to be "recovered". Meaning they take out the freon from your trucks system and save it instead of just releasing it into the atmosphere. Then they repair the leak, draw the system down to get as much air out of the system as possible . Then charge it back up. All that for about $1000.00+. By law they have to repair a leaking system. Anyway, that's most likely what's wrong. It's low on freon so the hi/low switch won't let the compressor come on.

[suburban_lee]

I'm a little concerned about jumping to the conclusion that low freon is responsible. It sounds like the A/C stopped working from one day to the next. There would have to be a substantial leak for this to happen, or a leak on the high side of the system.

The thing that clicks in and out on the compressor is the clutch. These can go bad. Here are a couple of tests to run to help narrow the problem down:

1) On the silver can (receiver / dryer) close to the firewall, on the passenger's side of the vehicle, there is a black wire harness. This is the connection to the low pressure sensor. Remove this harness and insert a jumper across the two leads. Try to run the A/C and listen for the clutch to engage. If the clutch engages, then you are very low on freon. Inspect for oil spots along the condensor and any of the narrow lines that lead to and from it (again, I'm leaning toward the high-pressure side of the system).

If the clutch does not engage, re-connect the harness to the receiver-dryer and check your fuses.

2) Assuming we still haven't pinpointed the problem, with the A/C controls set to On and the key in the run position (engine off), check for power at the compressor clutch. You'll need a volt meter to do this, and you can remove the two wire harness from the compressor and insert your test leads into it.

If you have power at the clutch and the clutch isn't egaging (am I spelling engaging right or is there a U in it?), then you have a bad clutch.

Good Luck!

[2000CAYukon]

The pressure cycling switch can also go bad causing the clutch to never come on. If the low pressure is good and jumping the switch causes the clutch to go, then the pressure switch is bad. They can be replaced without draining the r12.

//2000CAYukon

[wardriver]

Go to pep boys and buy a can of freon with the gauge on it. Hook it up, it will tell u if your low.

Just did mine, easy as pie.

[Ryan685]

Hey wardriver that's a good tip.