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2002 Chevy Trailblazer LT
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Discussion Starter #1 (Edited)
Hi,
So I have an 02 TB just crossed 150k the ac issue I’m having is it runs down to 45F and is usually fine unless the temp is hot outside over 80f. Or it will be cold for about 20/30 min then won’t blow cold. I have checked the Freon level it is full. The compressor will kick on and off. I have heard about getting the system pcm flashed By dealer. Where is the air intake for the cabin is it On the dash just outside the windshield? Also does the 02 TB have a high pressure cut out? Is there any sensor for cabin air temp? Finally does the ambient air temp sensor tie at all the the AC temp? Thanks again sorry for so many questions.
 

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My suspicion is a worn compressor clutch. Mine did the same. They can get stiff with age. A common way to temporarily deal with it is to remove a shim to decrease the "air gap" in the compressor clutch. Not a fix, but works for a time.

And yes, the 2002 has an A/C high pressure sensor. The PCM will disable the compressor when the pressure goes too high for any reason. One such reason can be a failing fan clutch. I've seen this cause A/C to fail in hot weather after the vehicle stops, or gets into slow traffic. At highway speeds the A/C works just fine but stop in traffic and bam,,, nothing but hot air.
 

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Ultimately - in all the seminars on AC.... the final say-so was the temperature of the compressor.
  • Pressure means very little in a R-135a system - not like it was with the older R12 gas.
  • TBH - it's all done by weight now and no - the cans you can buy are NOT 1-pounders!
  • They are usually short a few ounces to make thing harder for the DIYers.
  • There should be stickers under the hood for your particular vehicle - but somehow I don't think that will do you any good.
There MAY be an OVERCHARGE sensor - but maybe (read: LIKELY) not, since the systems are really harmed more by undercharge than overcharge, and pulling shims is indicative of something else going on - a different dynamic.
  • Get it idling - hood open - which is particularly hard on the system
  • Make sure you leave the windows open
  • Leave the blower on HIGH, full cold - front and rear if you have it.
  • The engine's cooling fan should be ON and that is also a good indicator of the system being up to temp.
  • The windows OPEN keep the thermal load on the system to a high state.
OK - now - and this is gonna sound oddball ---> you can use your hand to test the compressor for temperature and that'll indicate the state of the charge.

-----> the usual lawyer-type warnings and boilerplate apply here.... [lawyer talk]
  1. do NOT grab whirling, spinning, oscillating or rolling things of any kind:
  2. do NOT stick your hand - or anyone else's hand --- into a place where you think there might be just the slightest risk of losing that appendage forever!
  3. do NOT hold anything that is (either) too cold or too hot. {This should be basic to your infant training days - ask your mommy for clarification}
  4. Fan belts have to eat too - and they can see your hand and fingers! Be Ye Veri Careful ~ they await you!
  5. do NOT attempt to diagnose any mechanical problem if the vehicle is actually being driven at the same time.
  6. do NOT force your younger siblings - if you have any left, that is - into doing what you won't!
  7. Yadda, yadda, yadda and all that other lawyer-talk.
  8. You've been advised.
[/lawyer talk]

I know - I know --- it sounds crazy! --- but you are looking (feeling) for a compressor running at about 150-160° F - which will not burn your hand - but will be very uncomfortable to hold for too long.
  • If you can leave your hand on it for more than the amount of time before you get bored - it needs more R134a.
  • If you can't keep your hand on it for more than a second - or it's too hot to even CONSIDER touching! --- then it's likely overcharged.
All those dollars I spent and all the rubber chicken lunches I ate and all the days away from the shop to go to these seminars ------ <sigh> and the bottom line was: "If the compressor's too hot - it's overcharged. If it's cool or even cold - then you need more juice!"

OF COURSE --- since the systems have a LO-Pressure sensor - usually on the Receiver-Drier --- you will have to jump it out with a handy paper clip to make the system run if the compressor shuts off after a short run.

To say the obvious - I haven't actually serviced a TB yet - mine's running just fine --- but when I saw your post, I went out and did the same test and lo-'n-behold --- I could keep my hand on the compressor although it was SLIGHTLY uncomfortable.

You're looking (or 'feeling' really) to get an idea what your next game move is.

If I read between the lines in your post --- I bet you're system is too low on charge because the unit will stop cooling when the evaporator ices up and air cannot get through the fins if they're full of ice.
Overcharge can stop the compressor - and that's MY caveat tonight.
I don't think this is your problem, but I've been wrong before.

Low charge produces much lower than normal temperatures in the expansion-side of the system and it's not supposed to make ice.
Low temps = ice formation like an old refrigerator - but you're too young to know that. DE-frost time!
Low DEW POINT also helps screw things up..... watch out for that too 'cause it'll make ice a lot easier.
I digress.........................
  • Ice = bad.
  • No ice = good!
Of course --- here I am in Montana and I have NO idea where you are ---- and even if you hold the car up to the monitor/screen, I cannot truly diagnose it over the interwebs.

If you have one - you can use one of those hand-held, laser-type thermometers - but be careful there! They are kinda too accurate - but only just in the spot where you have it aimed!

You need a general overall temperature of the compressor and not just in one spot.

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

My next adventure in diagnosing low oil pressure in TB engines will require a baked potato, a tambourine and a jar of pickles. Wait for it!
 

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Yup... all well n good.... just make sure the air gap is truly the problem first. Run the temp test (my down-n-dirty one is a decent place to start) making sure you actually have a problem that's not charge related.

After that.... there's still a few more things that can be causing trouble. It's not one size fits all in AC repairs.

I only make this point to show that there are more things to go @SS sideways than just an air gap that might be too wide.

Several things CAN be the culprit.... not in any particular order of correctness.....
  1. Overcharged R134a
  2. Undercharged R134a
  3. R12 was mistakenly installed... or even R505! BT...SEEN IT...
  4. Too much oil
  5. Too little oil
  6. Wrong oil
  7. Pennzoil...... ok, I'm a LITTLE prejudiced!
  8. Inoperative engine cooling fan
  9. Mexican paper money in squirrel cage... yup.... saw that one once!
  10. Debris in condenser fins
  11. Worn out clutch
  12. Rodents ate the wires (don't EVEN ask! I still can see that when I close my eyes.)
  13. Superheat/Low oil sensor/ switch
  14. Thermostat on evaporator core
  15. Plugged expansion oriface
  16. Broken desiccant bag
  17. Incorrectly "satisfied" temperature setting(s)... usually a bad control on panel
  18. Compressor breaking up.... (sell car)
  19. "Cold Shot"-type products used instead of R134a (gums up oil) and/or can "slug" the compressor if it's injected incorrectly --- or at the wrong time --- or too much
Ya see... just sending an owner in to reset the air gap without him having first found out it is the cause and not a symptom, is gonna potentially cost time & materials by having him running in the wrong direction to get outta a tornado.

I opt for DIAGNOSE first ---- then throw money at it.

I've had a few mystery cars come it with absolutely the correct amount of freon, good oil charge, good blower fan, good cooling system, good compressor, good EVERYTHING ..... and still they would superheat and the head pressure would go high noon.

I had a 1963 Lincoln Continental come in for lack of cooling....... and everything was good! It would run a while and slowly build head pressure until the belt slipped and the cooling stopped.

I did all the right stuff.... this was a two cylinder, EPR system, God-simple and pretty foolproof.

Two days.... KNOWING I COULD FIX IT .... if only I could find the problem.....!

TWO. STEENKIN'. DAYS. and ..... nada! But I had a nice collection of used AC belts by now and nostrils full of rubber smoke.

On a whim, and because it was getting to be BEER O'CLOCK....
....I decided to go underneath on the hoist for a different look-see perspective, ya know ..
........ figuring that maybe ...
.......... .if the hoist fell on me ..... just a little bit...
...............I would be able to get outta the job.....
....................and as it was going up.... out of the corner of my eye ....
.......................I noticed that almost all the fins were missing from the condenser!

I couldn't even see the %&*!>⊙☆ condenser from above.... and to this day I don't really know why I decided to rack it up.... maybe angels! IDK --- just post game spitballing here!

The car was owned by a little old lady who drove like a bat outta hell ---back and forth from Anaheim to Las Vegas.... three times a week. The sand on the highway had eaten the condensor fins off and was working on the radiator now that the condenser wasn't in front, protecting it.

I learned then 'n there to diagnose and dismiss all practical textbook theories first... get 'em outta the way.... and use hard facts to pick the best hill you can find ..... on which you'll fight or die.

After the real theories are dead... then go off on any crazy idea of which you might think... 'cause you're only as good as the last job you did ..... and that one's gone..........

I feel a sage metaphor coming on.....

You can occasionally get away with shortcuts.

OK only one more metaphor, I promise.... when you shoot from the hip... you usually blow off a few toes and you run the risk of embarrassment, humiliation and a permalimp..

[/metaphors]
 

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Discussion Starter #9
Thanks for all the recommendations, I replaced the ambient air temp sensor. Not that that has anything to do w ac, level is full on Freon. Jumped low pressure switch. I think I am going to see if next time it’s hot and quitting in the heat try tapping the clutch plate to see if it will engage. If it does I am going to either remove or reduce the clutch gap with the shims and see if that makes any difference. I have seen a lot of videos of this working on older vehicles.
 

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Soon after we bought our Envoy , the AC quit . Everything but the compressor checked OK , it wouldn't engage .
I measured the clutch clearance . It was at the high end of the supposed acceptable range . I believe that range is .013" - .032" .
I pulled the clutch and found the outer face plate to be very uneven , due likely to rust . I smoothed that with a hand file and removed a .023" shim .
Put things back together and ended with a clearance at the lower end of the acceptable range .
Guess what . The compressor hasn't skipped a beat since and we have coooold air . ;)
 

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Discussion Starter #11
Yeah a lot of great recommendations here, my gut says to check out the clutch plate like you said. Clean it and maybe close that gap a bit. It’s not gna be over 85 here for next few weeks so I guess I’ll leave it alone and try tapping it to see if I can get it to engage when it should on a warm day. Hopefully it will kick on and give me a lead. Because it gets down to between 40-45 F just not on the days I really want it to lol was hoping to take it out on beach at least once this summer.
 

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Discussion Starter #12
Soon after we bought our Envoy , the AC quit . Everything but the compressor checked OK , it wouldn't engage .
I measured the clutch clearance . It was at the high end of the supposed acceptable range . I believe that range is .013" - .032" .
I pulled the clutch and found the outer face plate to be very uneven , due likely to rust . I smoothed that with a hand file and removed a .023" shim .
Put things back together and ended with a clearance at the lower end of the acceptable range .
Guess what . The compressor hasn't skipped a beat since and we have coooold air . ;)
how did you get to the AC clutch did you take off the fan clutch?
 

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how did you get to the AC clutch did you take off the fan clutch?
You can remove the outer part of the clutch to remove/add shims. It takes a special tool.

If anyone's experiencing clutch non-hookup.... check the electrical service to the clutch first. If there's no electricity, just remove the Molex-type connection and send B+ directly from the battery and ground (B-) the other connex to activate it before you go through the shimmin' stuff.

PS: this system doesn't cycle the compressor to control the pressure/suction. If your compressor IS CYCLING.... you've got a different problem.

..... just sayin' this to help people avoid rabbit holes......
 

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You can remove the outer part of the clutch to remove/add shims. It takes a special tool.

If anyone's experiencing clutch non-hookup.... check the electrical service to the clutch first. If there's no electricity, just remove the Molex-type connection and send B+ directly from the battery and ground (B-) the other connex to activate it before you go through the shimmin' stuff.

PS: this system doesn't cycle the compressor to control the pressure/suction. If your compressor IS CYCLING.... you've got a different problem.

..... just sayin' this to help people avoid rabbit holes......
Hmm , I had no special tools . Which one are you referring to ?
 

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Discussion Starter #15
I mean I can barely reach it from the top to get a socket on it the fan clutch seems to be really close to the ac clutch. How did you do it? I’m assuming the ac clutch is in the same location.
 

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I mean I can barely reach it from the top to get a socket on it the fan clutch seems to be really close to the ac clutch. How did you do it? I’m assuming the ac clutch is in the same location.
The AC clutch is attached to the front of the compressor .
Yes , I left everything in place except the belt . Turn the fan to gain the best advantage , as some blades are farther apart than others .
I used a large channel lock pliers , 16 , maybe 18" version , to hold the clutch wheel while I loosened the center bolt that holds the clutch together .
Careful to not loose any of the shims when removing the outer portion of the clutch .
I used a narrow magnet on a wand to fish out the shim I ended up removing .
 

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Hmm , I had no special tools . Which one are you referring to ?
I have the puller/insteller for the clutch... also the front seal puller/installer, but you won't get that far into the compressor.

On the versions with threaded compressor shafts, there's also another set of tools- one tool removes the circlips and retains then for reinstallation.

There's also a tool set for measuring the clutch air gap... you don't use regular steel feeler gauges 'cause they will lie.

AC work has so many special tools .... <gag me> ... that I had a lot of money invested in them over the years... and I still have most of them... especially for modern vehicles. Some of the early 1960s stuff is among the "gone" tools.

Innovation is always good and it seems you did it well.

Congratulations for a job done nicely.
 

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I have the puller/insteller for the clutch... also the front seal puller/installer, but you won't get that far into the compressor.

On the versions with threaded compressor shafts, there's also another set of tools- one tool removes the circlips and retains then for reinstallation.

There's also a tool set for measuring the clutch air gap... you don't use regular steel feeler gauges 'cause they will lie.

AC work has so many special tools .... <gag me> ... that I had a lot of money invested in them over the years... and I still have most of them... especially for modern vehicles. Some of the early 1960s stuff is among the "gone" tools.

Innovation is always good and it seems you did it well.

Congratulations for a job done nicely.
Thanks . I've always been one to work with what i had , before stopping by the bank .
We never had money , when I was growing up , so ... ;)
 

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Hi,
So I have an 02 TB just crossed 150k the ac issue I’m having is it runs down to 45F and is usually fine unless the temp is hot outside over 80f. Or it will be cold for about 20/30 min then won’t blow cold. I have checked the Freon level it is full. The compressor will kick on and off. I have heard about getting the system pcm flashed By dealer. Where is the air intake for the cabin is it On the dash just outside the windshield? Also does the 02 TB have a high pressure cut out? Is there any sensor for cabin air temp? Finally does the ambient air temp sensor tie at all the the AC temp? Thanks again sorry for so many questions.
if the air outside is colder it should not run it would stop just my 2 cents
But I have replaced my ac compressor the clutch went on mine too.
 

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Hi,
So I have an 02 TB just crossed 150k the ac issue I’m having is it runs down to 45F and is usually fine unless the temp is hot outside over 80f. Or it will be cold for about 20/30 min then won’t blow cold. I have checked the Freon level it is full. The compressor will kick on and off. I have heard about getting the system pcm flashed By dealer. Where is the air intake for the cabin is it On the dash just outside the windshield? Also does the 02 TB have a high pressure cut out? Is there any sensor for cabin air temp? Finally does the ambient air temp sensor tie at all the the AC temp? Thanks again sorry for so many questions.
You might want to look at your thermistor in side the hvac case they do weird things when they go out
 
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