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2002 gmc envoy_slt
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Discussion Starter #1
I went to see an auto air conditioning specialist today. My a/c turns on and off by itself. At first I thought I was low on refrigerant. He hooked up the a/c low and high sides and said they were good - 35 psi low side, and 175 psi for high side, so it meant I didn't need more refrigerant. Also, checked the low pressure switch and that was ok. Even tried testing it with a new switch but no luck. Instead, he told me something quite different - that the a/c clutch air gap had increased due to wear and tear. I guess after 192K the clutch wears out and the air gap increases and when the temp rises past 87 degrees (in my case), the clutch with almost never engage. He said that when it heats up, the magnetic part of the clutch loses its "strength" due to increased resistance especially at highway speed. The owner suggests to replace the entire compressor for about 800 bucks. I said no thanks, it's working fine. The specialist said he'll shim if so the air gap gets closer so it can engage the clutch easier even on hot days. Cost to shim the ac clutch is about 175 bucks. We'll see, I'm scheduled for tomorrow.
 

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I went to see an auto air conditioning specialist today. My a/c turns on and off by itself. At first I thought I was low on refrigerant. He hooked up the a/c low and high sides and said they were good - 35 psi low side, and 175 psi for high side, so it meant I didn't need more refrigerant. Also, checked the low pressure switch and that was ok. Even tried testing it with a new switch but no luck. Instead, he told me something quite different - that the a/c clutch air gap had increased due to wear and tear. I guess after 192K the clutch wears out and the air gap increases and when the temp rises past 87 degrees (in my case), the clutch with almost never engage. He said that when it heats up, the magnetic part of the clutch loses its "strength" due to increased resistance especially at highway speed. The owner suggests to replace the entire compressor for about 800 bucks. I said no thanks, it's working fine. The specialist said he'll shim if so the air gap gets closer so it can engage the clutch easier even on hot days. Cost to shim the ac clutch is about 175 bucks. We'll see, I'm scheduled for tomorrow.
Usually the clutch is the only thing needing to be replaced and not the compressor. The synthetic oil used is very slippery and shows almost no appreciable wear in most ac compressors over the lifespan of the unit. That is unless there were a leak from a seal and it was running dry. A ultraviolet dye that is green is added to the line to aid in identifying any system leaks.
 

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2002 gmc envoy_slt
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Discussion Starter #3
:DSaw the ac technician today and I'm confident the a/c is fixed! :woot: For those of you whose a/c shuts off when the weather gets hot, read on. I've been troubleshooting this issue for over a year. Like many you you TVers, I thought it had to do with low refrigerant charge or a bad low pressure switch. They both turned out to be fine. It never occurred to me that it could be the clutch. The fact is, the gap b/w the clutch and compressor, in my case, was greater than spec, about 3/32" or perhaps even as large as 1/8" most likely due to wear and tear, just like a disc brake rotor getting worn and thinner over time. When the a/c was turned on, you could see the clutch move ever so slightly trying to engage, but wouldn't. If we got lucky and watched it long enough, then it finally did. The a/c specialist removed the clutch and replaced the shim washer located behind the clutch with one that was thinner. The larger gap obviously was not allowing the clutch to magnetically engage, or at least it was intermittent, and when the ambient air was hot such as over 87' F, forget about it, the magnetic resistance is lowered and therefore the magnetic force is lowered, and that's why it never engaged over 87' F (in my case). That's what he said. So the a/c technician replaced the shim with one that was about twice as thin, and after he reassembled it, the gap looked to be about 1/16" or even 1/32". But the fact that it engages on demand is beautiful.:thumbsup: I have to say though, today the clutch behaved even before the service because the ambient temp never went above 83' F. So I'm still a little cautious:worried:, the true test will be this Sunday, when we drive inland for 8 hours where the temps are sure to be well over 90' F. I'll keep my fingers crossed. If this repair doesn't work, I think the wifey will divorce me:hissy: - the ac tech wants to save my marriage. :bonk:LOL.
 

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:DSaw the ac technician today and I'm confident the a/c is fixed! :woot: For those of you whose a/c shuts off when the weather gets hot, read on. I've been troubleshooting this issue for over a year. Like many you you TVers, I thought it had to do with low refrigerant charge or a bad low pressure switch. They both turned out to be fine. It never occurred to me that it could be the clutch. The fact is, the gap b/w the clutch and compressor, in my case, was greater than spec, about 3/32" or perhaps even as large as 1/8" most likely due to wear and tear, just like a disc brake rotor getting worn and thinner over time. When the a/c was turned on, you could see the clutch move ever so slightly trying to engage, but wouldn't. If we got lucky and watched it long enough, then it finally did. The a/c specialist removed the clutch and replaced the shim washer located behind the clutch with one that was thinner. The larger gap obviously was not allowing the clutch to magnetically engage, or at least it was intermittent, and when the ambient air was hot such as over 87' F, forget about it, the magnetic resistance is lowered and therefore the magnetic force is lowered, and that's why it never engaged over 87' F (in my case). That's what he said. So the a/c technician replaced the shim with one that was about twice as thin, and after he reassembled it, the gap looked to be about 1/16" or even 1/32". But the fact that it engages on demand is beautiful.:thumbsup: I have to say though, today the clutch behaved even before the service because the ambient temp never went above 83' F. So I'm still a little cautious:worried:, the true test will be this Sunday, when we drive inland for 8 hours where the temps are sure to be well over 90' F. I'll keep my fingers crossed. If this repair doesn't work, I think the wifey will divorce me:hissy: - the ac tech wants to save my marriage. :bonk:LOL.
You mean there's somewhere in the U.S. that 'only' reached 83?! We hit 100 in Portland yesterday! :weird:
 

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If it shuts off again when it gets hot you've got a bad clutch coil assembly. Coils heat up and one or more of the windings will go "open", (increased resistance) thus losing magnetic strength to engage the compressor. My air gap was fine so I had this problem and ended up getting a low mileage salvage yard compressor for $75.00.

I hope it is just the airgap for your sake. Please keep us posted......

.P.S. If it does cut out again, I'd try to work a deal with the A.C. shop to put that payment for the repair towards a new compressor if it comes to that. c good
 

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Discussion Starter #6
I'm located in the SF Bay Area and the temps the last couple of days have been mild. But come tomorrow, we're driving about 100 miles inland and along highway 5 it is always hot usually above 90' F. I'll try and post tomorrow night for an update. Also wanted to let you guys know that you can test your clutch by turning the ac on and using the lowest blower setting. If the clutch is working properly, you'll see it engage for about 10-12 seconds, and then disengage for about 6-8 seconds. It'll do this repeatedly and that is normal operation. Then when you set the blower on its highest setting, you'll notice the clutch almost never disengage as the refrigerant is always converting into a gas, whereas with the blower on the lowest setting, the refrigerant is only slowly converting into a gas so the pressure switch disengages the clutch to basically protect the evaporator from "freezing over". Don't mistake the normal cycling for low refrigerant levels. One should always check with gauges and the blower set on high to ensure the clutch is always engaged. Just my thoughts. :)
 

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The owner of the shop (different from the ac tech) said he only uses the best parts, which is either AC Delco or Delphi. He said to watch out for those "internet parts" :weird: :nono: and I just smiled at him :D. The technician suggested to replace the shim but didn't hear the owner suggest to replace the entire thing. Obviously, I wanted to do the shim service, then the owner looked kinda disappointed :( I didn't want to go for the whole shebang. When all was said and done, I gave the owner the $175 :raspberry and the technician a big fat tip.:thumbsup:
 

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The owner of the shop (different from the ac tech) said he only uses the best parts, which is either AC Delco or Delphi. He said to watch out for those "internet parts" :weird: :nono: and I just smiled at him :D. The technician suggested to replace the shim but didn't hear the owner suggest to replace the entire thing. Obviously, I wanted to do the shim service, then the owner looked kinda disappointed :( I didn't want to go for the whole shebang. When all was said and done, I gave the owner the $175 :raspberry and the technician a big fat tip.:thumbsup:
I definately understand the "repair" rather than "replace" mentality. I have had to replace a few compressors and have found that Ebay beats a lot of prices. The one I ordered for my Sierra was an AC delco reman with a years warranty. It came with all the parts that you should change when swapping a compressor, and it was $175. It was running fine when I sold the truck after 2 years. If it were me, I would replace it rather than repair it when the costs get that high. Especially with the mileage that that one has! 192k, someone is getting his moneys worth!:D


On another note, I had to call 3 shops to find one that was reasonably priced to do the vacuum, leak test, and fill the 134a. They understand that a broken a/c makes people desperate!
 

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Yup! Those are the symptoms of just a clutch. Some others include: works fine on startup, and shuts off and starts blowing hot air after driving a bit (like someone else said, once even more heat has built inside the engine compartment from driving for a while, internal resistance in the magnetic clutch rises, and then either a fuse or some intelligent circuit breaker flips), and of course, frequently blown fuses-- but the a/c works great in between replacing fuses. Sure signs of an electrical issue, and not the compressor itself at all.
A clutch is cheaper too, because there's no a/c evacuation and recharge, and depending on the car, the clutch can be done right on the compressor without pulling the compressor, so it's faster also.
As far as gap being too large, feeler gauges work great, and if you can see your compressor, you can watch it engage when a friend inside the car turns on the a/c-- or not engage, if the gap is way too large!



Yeah, dealership parts do end up being expensive, just being a retail outfit.
They buy from GM for $250 and then resell for $500 (just making up those numbers)-- where you can just buy online yourself for the $250, or less ;-)

But, they've got a supply chain, warehouse, shipping costs to cover, not to mention some insurance in case the new part comes in bad and they need to pay the mechanic all over again to reinstall. Not often, but it happens, so dealership prices have to cover the % of comebacks also.

I don't know about a/c compressors, but people do try to save a buck (or a couple thousand of bucks) by buying junkyard engines or transmissions, or a rebuild from the cheapest source they could find.
These things DO have a nonsurprising chance of a comeback, and the labor costs to redo them are expensive, when someone brings their own rebuilt or junkyard transmission, pays $1000+ to have it installed, and it starts slipping next month.
A friend at an independent shop went through 3 transmissions on a hummer when the customer brought in a rebuild he ordered online. First was slipping from the getgo, uninstall, ship the core back to CA and get another rebuild under warranty, pay for the labor all over again, same thing but after a week this time, ship the core back... wait for another rebuild... it's been a year now, I might ask if the 3rd time's been the charm. But it cost him 3 R&Rs because of the shoddy trans supplier.

If it had been the shop's own supplier, the shop would have been eating the pay for the mechanic twice over.

So it's also built in insurance and CYA when a dealership insists on only offering branded parts and their own in-house $5000 rebuilt transmissions. If a sleazy dealership started offering junkyard transmissions for budget-minded drivers, they'd lose their shirts on the comebacks. I know some junkyards even offer lifetime warranties on such components, but it would only cover the part with another salvage, and none of the significant labor charges.

Again, haven't done too many ac compressors (and failure rates on cheap ebay ones, which might not be bad, I dunno!), but another example is when I bought a $25 power lock actuator on ebay, made in china of course, thinking I saved a bundle over the $150 the oem version cost. Whaddaya know, it doesn't work. No power, can't pull the lock all the way down when unlocked, can't pull the lock quite all the way up if locked. Freezes solid when colder than 40F, and barely works in this summer heat. I did finally find some oem overstock on ebay, selling below cost I'm sure.
Can you really fault a dealership for charging $160, for a part that works?
If they offered people the option of the $25 (marked up to $50) door lock actuator, they'd be eating a LOT of comebacks; and the labor I'm sure is $100-$200 a door. And if I weren't doing it myself and eating my own labor time as it is, if I'd brought that $25 lock motor (x3 doors, actually) to a shop and had them install them, I'd be out $400++ in labor costs because of my own attempts to save a buck.

Just sayin'. Dealership prices aren't wholly unreasonable, there are reasons for them. It's mostly normal retail markup, 200%++ on little $5 stuff, 100% on most things, and at least where I work, big things like those $5000 transmissions actually have very little markup, <10% for example.
$30-$40 oil changes (depending on oil quality) have no profit margin; they're a convenience and a loss leader to bring in the other business that does pay. $800 for a compressor can be arrived at very easily; $250 marked up to $500, maybe 2 hours labor @$100/hr for the R&R, and another $100 for the a/c evacuation and recharge, and there you go.
 

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Discussion Starter #11
Well, drove for 8 hours today in not so sweltering heat as the highest temp was 88' F, but the good news is that the a/c never quit :thumbsup:. That makes me and the wifey and kids happy campers. To think that the clutch gap problem could be solved by replacing it with a superthin shim (prob 1/64") is an easy fix. If I knew about this simple fix I'd certainly would have tried to fix it myself but I hope I can share this experience so many others can do it themselves. I've already saved a bunch of money learning from all you TVers and how to fix everything in our trucks.:)
 

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Well as of now, we are driving from SoCal to NorCal and on the highway the temp reads 97' F and I'm happy to report the a/c is working all good and well!:D Problem solved! :woot:
 

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i am having the same problem with my 03 trailblazer

my 03 tb will do the same thing. it will work for a couple miles or when its cool outside it will work fine. when it heats up outside or you have drove for several miles it will cut off and not come back on until it sits for a while. i rebuilt transmissions for a living and have all the tools for ac work but when it comes to ac i am not very smart on.. i have evacuated the system and put a new orfice tube in and refilled ac to specs. the gauges are ok and i also replaced the electric fan clutch. i have had a couple people tell me that i have to have it reprogrammed and some tell me that i dont have to. should i have it done or not? also how much should the gap be on the compressor clutch? i think that its my problem but i dont know exactly how much gap it should be. also i have a 99 firebird thats my wifes car and when you get in it to start it sometimes the security light will come on and you have to wait for it to go off and then it will start sometimes and sometimes you have to wait again. i have replaced the ignition switch 2 times and had a couple keys made for it. i know this is not the right place for firebirds but all of you are smart on all this other stuff i thought i would see if i could get some help on it to maybe, the car seems like it does it worse when its either raining, damp outside or its really humid. i live in west TN and the humidity is killer here. I appreciate any help in advance.
 

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Don't know much about Firebirds so I can't help you there.

I DO know about TrailVoy AC systems. After confirming correct operating pressures as you have, nex you always want to check Low Pressure cut out switch. When compressor cuts out, jump the L.P. switch to see if it is the cause of the problem. If it's bad, when jumped, the compressor will turn back on. If it doesn't then it's probably a weak/bad clutch coil assembly or too large an air gap. A way to test for a weak clutch/coil assembly is to take a broom handle and CAREFULLY push in on the front of the compressor/clutch assembly. If it grabs then you know you have too much air gap just as previous poster.

I want to emphasize.....BE CAREFUL when doing this. Do not get the broom handle tangled up in any of the other components. If it doesn't engage then you have a bad clutch coil assembly all together. Time of for a new compressor.

The reflashing of the software will not solve this problem. HTH keep us posted. c good
 

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Keith81 I think that there is a security solenoid in by the key somewhere. The leaving the key on for about 10 mins is to reset or resink the key with the security device. My parents are having this issue with their 02 malibu. Not sure if it is your problem but sounds close.
 

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Keith81 I think that there is a security solenoid in by the key somewhere. The leaving the key on for about 10 mins is to reset or resink the key with the security device. My parents are having this issue with their 02 malibu. Not sure if it is your problem but sounds close.
so what do i need to try to do? just turn the key on and let it sit for 10 mins. not do anything else but that? thanks for the help on this. its driving me crazy
 

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Keith81 Yes that is all I did to my dads car and it worked. It was in the manual for the vehicle. It has happened again since then so it may be the security solenoid but for now it is ok.
 

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Discussion Starter #20
I DO know about TrailVoy AC systems. After confirming correct operating pressures as you have, nex you always want to check Low Pressure cut out switch. When compressor cuts out, jump the L.P. switch to see if it is the cause of the problem. If it's bad, when jumped, the compressor will turn back on. If it doesn't then it's probably a weak/bad clutch coil assembly or too large an air gap. A way to test for a weak clutch/coil assembly is to take a broom handle and CAREFULLY push in on the front of the compressor/clutch assembly. If it grabs then you know you have too much air gap just as previous poster.

I want to emphasize.....BE CAREFUL when doing this. Do not get the broom handle tangled up in any of the other components. If it doesn't engage then you have a bad clutch coil assembly all together. Time of for a new compressor.
:iagree:That's a great idea.:thumbsup: The ac specialist used a wrench to tap it in and it engaged fine, but before it engaged, if you watch the clutch closely, you could see the gap close a bit trying to engage but wouldn't only when the outside temp was over 86' F. Cooler than that it engaged normally. It just needed a nudge and when tapped it did engage nicely. I agree that if it did not engage, then a bad coil assembly would probably be the culprit.:yes:
 
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