2003 Trailblazer - a/c air conditioning intermittent

[mmagliaro]

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.

[rodeo02]

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

[mmagliaro]

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.

[maxwedge]

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

[mrc651]

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.

[mmagliaro]

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

[mmagliaro]

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.

[maxwedge]

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

[mrc651]

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.

[mmagliaro]

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.

[mmagliaro]

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?

[Jethro]

Originally Posted by mmagliaro

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.

[mmagliaro]

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.

[maxwedge]

Get the updated one from GM.

[mmagliaro]

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.