b2breese

My '20 Suburban blows heat with the fan control off and the thernostat turned down to cool. This tends to happen on longer trips as we are not affected by it on short trips. We drove 300+ miles this weekend and could not take the heat. We stopped at a rest stop for 15 minutes or so and when we resumed our trip cool air flowed and the heat stopped, almost as if it reset something. I also do not think that the AC is working./It is intermittent and my mechanic told me that he cant fix it if he cannot make it happen again. Any ideas?

48fan

Well for one you have a lot of area to cool in a Suburban. The color of your interior (dark colors) and the fact that you have so much glass around the truck makes it like a green house; your windshield is your biggest source of heat. As far as the hot air coming through the vents goes, you are going to get engine heat coming through your vents. I can't answer for the reason the heat stopped when you got out to take a break.

Try switching to defrost if you don't want air coming through the vents. Otherwise you need to roll your windows down if your A/C doesn't work.

If you are more specific I can help you find your A/C problem. When turn on your A/C what happens? Any sounds? What’s the air temp coming from the vents?

4re4me

The exact same thing is happening on my 2001 Suburban. It is intermittent, but incredibly uncomfortable when it occurs. It happens after I have used the heata little, but then turned the temperature selector back to cold. Not only does it not get any cooler, it actually gets hotter and seems be even hotter than when it is normally on the highest temperature selection. Turning the fan off and on does not do anything and it is even very, very hot with the fan all the way off. Changing the selection on all the dials, redirecting the flow, etc. does nothing. But, shut the truck off for a few minutes with the temperature selector set to cool and it "resets". I haven't taken it in yet but, if anyone makes progress on this, please post. This seems like a sensor or computer chip or something. I hope you don't have to remove the dashboard to get to it.

vf171

2002 Suburban here, 2500 LT 8.1L. Automatic Climate Control

Air started blowing very warm a couple of days ago. I checked pressure in system and read zero so I thought it had a slow leak. I put a can in thinking I would pay attention to how long it lasted. My wife drives it and isn't the most attentive and I don't trust her when she says "it started happening all the sudden...” Anyway I put a can in and checked pressure again - zero psi. So I tapped another can and opened it, shut the engine off to listen for obvious leaks. Found one, I think.

There is a plug on the back of the compressor that hooks to a sensor/switch of some sort. I've searched available parts diagrams but none clearly show the part I'm looking for. Anyway, it is melted! I can't tell if it melted in the compressor and fell offor if it broke and then lay on the exhaust cover and melted. There are no signs of melted plastic on the exhaust cover.

I used an inspection mirror to look into the cavity that the switch/sensor obviously came out of. The front part of the switch is still in there and I don't see signs of melting on that end. So I'm guessing it somehow broke and melted after it fell out. I called a Chevy dealer in the town I work in and described the part to them and they said it sounded like an A/C pressure sensor but they didn't have one in stock. So I called the dealer in the town I live in. They had a High Pressure Side Sensor (02724976) in stock. I picked it up but now I'm not sure it's the right part. It's shaped like the one I have (at least the back half) and it appears to be the right diameter to fit into the opening on the compressor body. When I do a search on the net the only place it shows up is on Rock Auto's site and it's listed under the '99 GMC Sierra 2500HD. I looked under the '02 'burban but it doesn't show up there.

Now I’m confused. I have a part that doesn’t show up on anything I’ve looked at so far and the front half of the sensor is still in the cavity so I’m not so sure it’s leaking there. The new switch I got came with a new o-ring and internal snap-ring but I don’t see those items anywhere on the compressor.

To boot, the new switches plastic body is red, the old one is purple. I know sometimes OEM’s color-code there stuff for assembly line quality purposes but since this appears to be a non-OEM part I guess they are free to use whatever color they want.

I’m hoping someone out there will know what I’m talking about and the same time I guess I’m suggesting that those of you with ACC and having this problem may want to look into this switch and make sure it isn’t failing intermittently and a vehicle shutdown/restart isn’t resetting the switch.

Thanks in advance.
Phil

southern slammer

hey vf171,
The switch that is broken off in the back ...is the high pressure cycling switch electrical connector ,i would replace that and check to see if your orifice tube is not clogged in anyway which this will mess with your system performance.

vf171

Ok, I rpelaced the switch. What a PITA!!! Anyway, it' in.

Here's where I'm a little confused though. I added a can of refrigerant thinking the system was empty. I put the gauge on and it registered ~40psi. Surely a 4oz can isn't all this thing takes? If not then I guess the refrigerent wasn't leaking out of the system as I thought it was and it was blowing hot only beacuse the cycling switch was broke.

Here's the background info I should have given to begin with. A couple of weeks ago the compressor would click when the clutch was engaged. I should have pulled it off then but I haven't had a bunch of free time lately. Anyway the clicking stopped then we noticed the warm air a couple of days later. That's when I found the broken switch.

Now that I've put the new switch in and the compressor clutches are engaging again the clicking noise is back and the system still blows warm air. Like I said, I'm at just a bit above 40 psi which is in the yellow region of my gauge. Is the location of the orifice tube easily explained? I don't know what to check to make sure it's not blocked. From what I can tell this serves the same purpose as the thermal expansion valve, is that correct?

I'm going to take it to a garage next week if I can't figure this out on my own. My wife drives our kids everyday in this thing and it's supposed to be 85+ degrees and humid. I can't waste too much time on this, I feel terrible everytime the kids get out and are drencehd in sweat. Any help would be appreciated!!

Thanks.

vf171

I just went out to check the pressure again. It was reading zero psi. I noticed the compressor clutch was not engaged. I checked the switch again, it's broke again.

That switch is extremely heavy duty plastic, I can't figure out how it's breaking. The sensor portion of the switch is still in the compressor but the electrical connector portion is the part that is breaking. One theory I have is that the fluid is somehow leaking past the o-ring and freezing the plastic making it very brittle.


Anyone have another theory?

vf171

Just thought I would share my findings...

I took the truck to a local mechanic (A/C & Radiator specialist) and he found the root problem. The engine fan clutch was bad. Apparently if this clutch goes bad (not out, just bad) it doesn't cool the freon in the condenser which is in front of the engine radiator. That means you'll be getting either a mixture of gas and liquid or worst case only gas to the compressor. As I'm sure most of you know, the compressors really don't play well with gas. They're designed for fluids.

Long story short, things got pretty bad in the compressor and it pretty much grenaded internally. He said the orifice tube was full of aluminum which was an indication that the rest of the system was littered with it as well. He replaced the fan clutch, compressor (new, not reman.), orifice tube, and dryer. I haven't seen the parts list yet, my wife picked the truck up last night so there may be more. I just asked to fix it right, no half-a$$ fixes. The temp. here has been in the upper 80's-lower 90's and pretty high humidity. Since my wife and kids are in this truck everyday it had to be done right. I can live without A/C, they can't

Total bill was $1200![:'(]

He also flushed the entire system, steamed the engine and put dye in the system then ran it for an hour. No signs of leaks elsewhere in the system. It blows cold now. Man I hope this doesn't happen again! Had we bought the warranty when we purchased the truck (we bought it used) it would have almost paid for itself. Oh well. [&o]

Keep an eye on those fan clutches. The guy who owns the shop and worked on my truckdrives only Chevy's and he said he sees this somewhat frequently. I would have never thought to look at that.

vf171

Yet another update. Seems while I was out running this afternoon the wife decided to take the kids swimming. She started the truck and turned the A/C on. She said she seen a puff of white smoke and heard a sound like a lawnmower and stuttering. She shut it off and it ran fine to her mom's place with no A/C.

I went over and checked it. It didn't do anything wied for me but it's not blowing as cold. I'm thinking the orifice tuube is plugged again. Can someone tell me where to find it?

Thanks.

golfer

That's a little backwards. The compressor likes the gas not the liquid.

A little basics here :
The return gas from the evaporator coil ( inside the vehicle ) goes to the compressor.

The compressorcompresses this cool gas whichbecomes under high pressure and sent to the condensor.

In the condensor the gas condenses into a liqiud then goes to an expansion valve where it evaporates to become a cold low pressure gas and then goes on to the evaporator to start the cycle again.