2003 Trailblazer - a/c air conditioning intermittent

Oh boy, is this going to be a pain. On our '03 Trailblazer EXT, which has performed flawlessly until now, the a/c started randomly not working.
Sometimes the compressor will start, sometimes not.
Sitting in the driveway the other day, I started it, and the compressor kicked right on. The outlet temp at the vents went right down to 40 degrees F, which is very good.

We took it to be serviced today (at the dealer, but we have had magnificent reliable service from this dealer, believe it or not), they said they could not find anything wrong with it. The compressor is working, the refreigerant is not low, and there are no leaks. They said it came right on and cooled every time they tried it.

This smells to me like some annoying electrical intermittent problem - I know there is a fuse in the fuse block. Are there some other hidden relays in the circuit to the compressor? Any notorious connectors that go bad?

I've read a whif of complaints about flakey Trailblazer air conditioning on the web already, so it looks like I'm really in for it until it gets so bad that it won't ever run. Then, maybe the service garage can fix it.

Thanks to anybody with ideas.

Does the A/C only poop out when the truck is hot? Bad radiator cooling fan clutches are a common failure point. Trailblazers do not have adequate cooling fans for super hot conditions.

Joel

I can't be sure about that. If the fan clutch is slipping, would that cause the
compressor to not turn on? Because that's the problem. It isn't that the compressor runs and there isn't enough cooling. The compressor does not
turn on, period.

I wouldn't think that the fan clutch could cause the compressor to not energize, could it? Maybe there's something about this car I don't realize.

I will start paying close attention to the times of day and the temperatures when it works and when it doesn't.

Lo/high pressure switch was problematic in many TB's. TSB was issued in late 2002 for this condition.

that happened to my 2003 T/B a few years ago when driving back from Hershey PA to Northern NJ in August!! It was the Lo/High switch.

When the Low/High pressure switch failed, did your a/c still work sometimes, or did it just flat-out quit working?

I did some reading around now, and found the GM bulletin on these problems with the Low Pressure Cycling Switch. That really REALLY sounds like what this is.
The GM bulletin (03D-J-128) doesn't show a diagram of exactly where this thing is and what it looks like. Can anybody point me toward a diagram or photo of it, or describe to me where it is?

Second, various accounts of people replacing it (on the web that is) indicate that it is just screwed on over a Schrader valve, so that it can be unscrewed without losing any refrigerant (well, a very tiny whiff as you pull it off the valve, but nothing more). Is that correct?

Thank you.

Yes and it should be in the lp line, just trace it and you will see where it is .

Sorry have checked the bored in a few days. With mine the A/C would work then stop working then start again. It was an intermittent thing.

That seems to be what's going on here. Since I posted the problem, it has not done it once. Dang thing works perfectly every time, outlet air temp is about 42 degrees F. Sooner or later, I'm sure it will quit again, so I can try tapping
on the pressure switch or bypassing it.

Thanks.

Okay. It finally did it again. Was working fine as my wife drove home,
then spontaneously quit working (compressor cycled off, and outlet temp
rose to about 65 degrees F).
She got home, left it running in the driveway, I went out,
tapped on the side of the lo pressure cycling switch with the butt end of
a screwdriver, ---- "CLICK" ---- on goes the compressor,
down goes the outlet temp to about 45, and the pipes
got cold and frosty again.

Where do I buy one of these? All the auto stores like NAPA, Pep Boys,
Autozone, do not list this part at all. Do I have to go to a GM dealer to buy
this part?

on goes the compressor,
down goes the outlet temp to about 45, and the pipes
got cold and frosty again.
If yours pipes get frosty you either have blockage in the condenser or you are low on frigerant.

Well, that depends on what you mean by "frosty". I have probably misled you. They do not get covered with white snowy frost. They just get very cold and there is a dull-colored look to them. That's how they have always been. That's how my '98 Silverado pipes get, too, and that systems works.

I'd say since it works for hours on end (except for when this kooky intermittant thing happens), and the outlet temp is always between 40-45, it's not a refrigerant problem. That, and I did have my repair dealer check this, and it was not low and there were no leaks.

Get the updated one from GM.

Well, I found one at NAPA after all. They don't have it listed on their website, but the stores have them. It cost $28. Unscrewed the old one. As advertised, it is definitely on a valve so you don't lost any refrigerant when you unscrew it. Put the new one on. Works perfectly. A/C is fine now.
Thanks everybody.

Glad you're good to go on that low switch. Yeah, it's a common poop out on your model year. GM did issue a replacement. Many dealers will replace for free in or out of warranty if you set it up via GM customer svc. It's not like trying to get GM to replace the fan clutch after the warranty expired.

I just noticed mine doing something similar...1st real hot day here. MIne seems like it takes a long time to cool, especially the rear air, however the front takes a while too. Also noticed a clicking sound coming from engine compartment. No time to track down source of click yet. It was a steady clicking, it stopped before I could get the hood up to investigate. Sounds like the same thing discribed here. Where exactly is this Lo/High switch located? Max said trace the lp line, is it the line that runs to the drier on the right just aft of the air filter box?

I meant accumulator, not drier. Does the lo/high switch screw into the side of the accumulator? Rockauto has pics of various GM sensors & switches, not sure of what I'm looking for though. Would this switch cause the symptoms I am having as per my discription? Sounds close to what others have described on this thread. I know the lines don't feel very cold to the touch, today was the 1st day I heard it click like that. How often should the system be recharged with refrigerant/oil? I would think if there is no leak it shouldn't need evacuated and recharged. I am not very good with HVAC systems, need your help guys. Thanks Carp.

The compressor occasionally cycles off and on, and you will hear a click when it does this. If it's doing it a LOT, and that's what the clicking is that you hear, it COULD be this switch, but it could also be low on refrigerant. You should take it to a service garage (if you can't do this yourself) and have them check that the refigerant is full and that there are no leaks. They can inject an ultraviolet-sensitive dye into the system, and then shine a blacklight on it to look for leaks.

You can get a simple to use kit at auto parts stores that comes with a gauge and a can of refrigerant-and-oil-in-a-can. It will have instructions telling you where to screw the gauge on and how to read it. If it's low on refrig, you can add some with the kit. If that fixes it for a while, but the problem comes back in a week or two, you definitely have a leak, and you need to get it fixed.

If the system is full, and the compressor still doesn't run (and you get warm air), then you can think about the switch. The switch is on the passenger side of the engine compartment, near the firewall , screwed into the side, near the top, of a large silver metal vertical canister (I think this is the drier/accumulator). It looks like a small plastic cylinder with
a 2-wire connection on the end of it. The 2-wire connector pulls off, and the switch itself just unscrews from a connector. Just as you pull it off, you'll hear a quick "sssssst" of gas escape, but no more. The switch is screwed on to a schrader valve that will close when you remove it, so you won't lose refrigerant.

I determined that mine was at fault because I KNEW the system was full, and it would go warm for many minutes, so I was able to rap on the switch with the rubber handle of a screwdriver, hear the compressor click on, and STAY on, and that pretty much convinced me the switch was hosed.

Thanks for all the helpful info. I need to have the system checked for low refrigerant anyway. Who knows when this was last done. Only had the truck for about 6 months & it seems all the preventive maintenance was neglected. I am slowly working my way through it all though. Hopefully a recharge is all it needs, but will keep said switch in mind if not. I sure appreciate you pinpointing it for me. Thanks
Carp

Not a problem. I had to recharge my 1998 Silverado 2 years ago. It was 7 years old with about 100,000 miles on it. If it does have a leak, it would have to be awfully slow because I haven't had to do it since, and it still runs cold.

It was not cooling well at all. I bought one of those kits, checked the pressure with the gauge, and it said it was low. So I added "some" (about 1 can), then checked the pressure and it was in the middle of the "good" range.

This is definitely a homeowner-style fix with these kits, not as precise as they'd do in a service garage, but it does the job.

Yes, that's where/how you R/R the hi-lo switch.

On that clicking sound, I hope it's just the compressor kicking in/out due to a defective switch. But a clicking sound from under the hood, particularly at start-up, is also associated with a failing fan clutch. It seems every '02-'04 Trailvoy owner in America has experienced it or will. The other common symptoms of a bad fan clutch are a jet engine-like howl at the front of the engine and the transmission requiring extra-high revs to upshift. Many owners have mistaken a bad fan clutch for a failing transmission. Good luck.

:bloated: :banghead: I need help. My AC went out aprox Dec of 2005. the system to the back seat blows cool air, the system to psgr side blows cooler air ( not cold ) and the system for the driver blows hot air. This was the way it was acting in 2005. I checked the refrig and it showed full. At that time the repair shop where I had it fixed said it was the controls inside the dash. That cost me aprox $1100.00. I now am having the same problem and the repair shop that I took it too said it was a leak in the evaporator. And it would only cost me aprox $850.00 to fix it again:( ??? I checked the refrig today and when the compressor is not kicking in the gauge shows in the blue, when the compressor IS kicking in the gauge reads almost in the red, which with my limited understanding means the system is full and there are no leaks:disappoin> does anyone have any ideas???

Mine only clicks after it has ran for a while and only on the hotest of days. I am familiar with the fan clutch symptoms and am sure that is not it. (yet) I drove a brand new Ford 15 pax van this week at work and my TBs ac was WAY colder than that! That thing only had 1,400 miles on it and at idle it was barely cold at all. It definatley sounds like compressor clicking, it may be normal, but it is pretty loud. I am leaning toward the Hi/Lo switch, something for me to keep in mind if it gets worse. Thanks for your input.

To Walter Joe Stanley....if the a/c is blowing cold out all the vents but the drivers side, the problem is not with refrigerant. Chances are there is a bad mode actuator or temp door actuator in the airbox that is not directing the cold air properly. In my experience, this is a job better left to the dealership. They can diagnose and install this much easier than a shadetree...or most of us common folk.

when i start the truck it take a while to cool u think it's the low/high switch

My 2008 Trailblazer AC works intermittently, and at the same time the ac doesn't work, neither does my engine temp gauge. When the gauge starts working, so does my AC. When working the AC does a good job of cooling. Is this a major electrical problem?

thanks to all who contributed to this topic. My 2002 GMC Envoy has the same intermittent problem. I took it to the Chevy dealer that services my car and asked them to replace the Hi/Lo switch.

One thing to note is that not ALL of these cars (TB and Envoy) have the pressure valve that prevents the freon from escaping. Mine didn't have it, so the system had to be evacuated and refilled. So do be careful if trying to make the repair yourself.

Now to see if that actually fixes the problem <grin>

Have to be careful when jumping on old posts......

We have gone from a 2003 TB to a 2008 TB to a 2002 Envoy.....and the 2008 was a different problem.....

As for the Envoy, there is not a hi/lo switch, only a low pressure switch......it also has a 3 wire pressure sensor.....

Make sure you have enough refrigerant before replacing the low pressure switch.....

ok we have had several vehicles that a/c works fine at idle, then as you give it gas , the a/c stops,
1. low on Freon, 2.bad pressure switch, 3 fan not working ,or bad, fan switch bad, 4 high pressure default, 5, bad a/c compressor clutch.. 6 lines in a/c restricted or clogged, 7 bad orphis valve or tube, 7 restricted a/c condenser, 8 electrical fault,

the last trailblazer had been worked on by the owner and they had the orphis tube in backwards, this caused the a/c compressor to build high side pressure and kick the switch out , we removed it, cleaned the system and replaced, it , vacuumed and recharged..