TrailBlazer AC Clutch not engaging.

NickD

wrench
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Aug 28, 2007
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I hook up my metered power supply directly to the clutch coil, vehicle connector removed. Set it for 14.5 Volts and read the clutch current, should read around 4 amps. Let it cook for awhile, the coil heats up and that current should drop. Since it is a random wound magnet wire coil, heat can causing intercoil shorts, current then goes up. Bad coil.

Power supply lets me adjust the voltage, with a cold coil, expect it to engage at around 9-10 volts. Most coils that read a cold 4 amps at 14.5 volts should only drop to around 3.5 amps after heating up.

Using this with the engine running at 1,500 -2000 rpm gives me complete manual control of the system with manifold gauges attached. If the high side jumps and even starts to approach much over the rated high side pressure, under 300 psi, and up to over 400, instantly switch off the supply.

If everything works normal, pressures and cooling is good. clutch is good, but still problems, its electrical in the vehicle. That is were the fun starts depending on the vehicle.

Clutch coils can be good and the problem is with the clutch disk itself, if a leaf spring type, can be a pile of rust. Some idiot disks use a piece of rubber for that, that dries up harder than a rock, with those, try and find a leaf spring replacement.

Pricing is also ridiculous, in buying just a clutch kit for just a few bucks more can buy the entire compressor with a new clutch kit installed. But if the basic compressor is good, really a PITA to change it, have to recover the refrigerant, flush the system, replace the accumulator/receiver, draw a deep vacuum and inject clean dry PAG. Have to keep the EPA happy. they don't give a damn about your misery, just trying to preserve the earth on false theory. But now saying R-134a is bad. Since they all drive government supplied brand new vehicles, they don't give a damn about the rest of us. Most I know also drive these free vehicles for their own personal use.

Heck, get a job with the EPA, only requirement is that you have an IQ of less than 2!
 

NickD

wrench
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but you guys probably have plenty of money anyway.
Would have, if we didn't have to pay $6,000 a year for property taxes, only service I am aware of is picking up a half a bag of trash each week. Did buy a new vehicle with $5,500 in rebates, but still had to pay the state 300 bucks in extra sales tax. We spent $12,500 in state tuition last year, but could only deduct $4,000 of that off our income tax. And that was after they already cleaned out our gross wages with FICA taxes that we also had to pay both state and federal income taxes on. Then another $14,000 for health insurance. College says all the state and federal money is going to Iraq to fight for their freedom when they don't even want us there.

Food prices are ridiculous since they started burning food for ethanol that isn't worth a crap and using just as much fossil fuels to make the stuff. Gas is not 4 buck a gallon, with much lower BTU ratings, cost more like $5.40 per gallon, but can't even deduct that for driving to work or school.

Then have to pay taxes on our savings with only 1% interest, when government caused inflation says that money is worth more like 5% less, they don't consider the cost of energy nor food in their inflation estimates. More like the price of Made In China junk that is on sale at Walmart.

After both direct and indirect taxes, we are well below the poverty level, but the government says we are rich so tax the living hell out of us.

I recently rewound a defective clutch coil to save a few bucks, have to do something to have enough money to buy food.
 

year.0

Newbie
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Jun 29, 2020
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I just removed a shim on a 2002 Traiblazer compressor yesterday-- the clutch was pulling in slowly- one side then the other-it gave a double click upon each engagement- this too is a sign of a wide worn air gap--The owner had the same complaint as you folks-- no air after it warms up...Only trouble was that I had to remove fan and shroud to access front of compressor - then just remove the 14mm bolt from front of compressor, wiggle clutch driver out, then reach in with a magnet and pull out the shim- then re-install the clutch driver. I did not bother to measure air gap-- I only care than clutch does not rub when not engaged- and that pulley spins freely. Why buy a clutch when removing a shim works great? Do what you want- but I don't advise spending money you don't have to-- but you guys probably have plenty of money anyway.
I was having this issue with my 08 Envoy 5 3, tracked the problem down to the compressor but didn't know I could just pull a shim and fix it. THANK YOU!!! Taking a 1000 mile trip for the July 4th weekend and was thinking I was going to have to spend a few hundred dollars and a few hours to get it working. Pulled the fan and shroud to access the compressor and pulled the shim and viola, cold as ice all day. Your posts here saved the day!
 

NickD

wrench
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Aug 28, 2007
Messages
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10 mils was a good clutch gap, the pulling in magnetic force decreases by the cube of the distance. Now have to think about shims with GM, pressure plate was a so-called interference fit or shrink fit. Over the years GM changed the installer/remover tool, so had to buy three different ones of them. Do recall shims back in the 60's. Did they go back to shims?
 

brcidd

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Nov 16, 2006
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Any service center would have replaced the compressor---they do not "fix" anything, only replace parts. You had a choice, $1100 for a new compressor, or $0 for a shim removal. Sure feels good to help someone in need....and to know exactly what went wrong. I lived and breathed this issue ever since the latest shim designs came into being. The key is the description of the failure mode. I've seen tons of them- on any compressor that sets the air gap by using shims. So knowing, researching, your compressor is paramount. So glad this old post got some traction and you were able to fix it yourself. Isn't the internet wonderful?
 

NickD

wrench
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Aug 28, 2007
Messages
5,162
Points
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Any service center would have replaced the compressor---they do not "fix" anything, only replace parts. You had a choice, $1100 for a new compressor, or $0 for a shim removal. Sure feels good to help someone in need....and to know exactly what went wrong. I lived and breathed this issue ever since the latest shim designs came into being. The key is the description of the failure mode. I've seen tons of them- on any compressor that sets the air gap by using shims. So knowing, researching, your compressor is paramount. So glad this old post got some traction and you were able to fix it yourself. Isn't the internet wonderful?

Shops have to do over component installation, have to if given you a 30 day warranty. Many friends came over after spending a fortune having many components replaced without curing the problem and charge at least 30% than what you could buy the component for. When the real problem is a loose manifold bolt, corroded electrical connection, or a leaking vacuum hose. Sure took advantage of my wife, after marrying me, saved a huge fortune on automotive repairs, not going to tell you how she pays me.

Sure sure screwed my daughter in that phony emissions test in the City of Milwaukee, just hook up a two buck scanner, if they see no codes, charge you 50 bucks and give you a sticker for your windshield. I just put on a genuine GM single belt on that car that cost me ten bucks. They said it was bad, its going to break, can't drive your car and you are going to die freezing to death. Put on a POS made China replacement belt and kept my belt. Probably sold that one to some other sucker for $200.00.

Don't even get me started on wheel alignment shops.
 

MrConspark

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Sep 29, 2020
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Sounds like you did almost everything except the most obvious and common cause of this. Check the clutch gap. Been a problem with GM AC compressors ever since some nitwit elected to use an interference fit for that clutch plate. It either closes the gap so the compressor is running all the time or just getting red hot from friction or more common widens so the magnetic field that decreases by the square of the distance can't pull it in.

If that isn't bad enough, need a special clutch plate remover and installer tool, wouldn't be so bad if they left that same, have three different ones already, keep on changing the threads. Understand places like Autozone loan these out, either buy or make my own.

Reason why you need these tools besides setting the gap, I prefer 20 mils. (0.020") is to remove that clutch plate so you can get at that cheap idler pulley bearing, never had problems with these when GM was putting the AC compressor on the top of the engine and even using a retainer ring. To add to the misery, they are peening that bearing in now. Never have good success in repeening it with an older idler pulley, that cast iron like glass hardens with age, chips off instead of forming a new peen. So end up using flat head screws countersunk to catch the outer race of the bearing.

Another reason was with all this new EPA BS, GM quit using a perfectly good ceramic seal and switch to a neoprene single lip seal, finally went to a double lip seal sometime in the late 90's, that could also be changed with the compressor on the vehicle. But mostly on R-12 systems. With R-134A and PAG, better off to remove everything, drain and flush the compressor with PAG, drain that out, flush out the entire rest of the system, replace the dryer, draw a deep vacuum, and then inject the PAG, but only from a tin can. If the slightest bit of moisture gets in there, forms acid, then you really have major problems.

Correct amount of oil started in the early 60's when GM dumped the York compressor that had an oil sight glass on it, one glance and you were done. Only way to do it right is to flush and drain and put the correct amount in. Lot of other guys add a couple of ounces, I don't do work like that, just guessing. Too little and your compressor will seize, too much, reduce cooling capacity or even oil slug the compressor and wreck it.

Also had to get myself 608/609 EPA certified so I can buy a can of R-12, R-22, or even R-134a in Wisconsin. Not a damn thing about AC, just proper recovery and disposal, but with the crap on the market today, never had to recover, when I see it, all that refrigerant is already gone. EPA has zero restrictions on the manufacturers of this crap.

Not ranting, just telling you the way it is. If a car is decent, will spend 600-700 bucks and buy all new stuff, can't even flush a parallel condenser anymore. If the car is not worth it, just roll down the window and get the last few miles out of it.

Too even further complicate this field, EPA permitted the sale of all these substitute refrigerants, not because they are good for your system, but because they they meet their ozone depletion standards, this flooded the market so now you need a refrigerant identifier to learn what kind of crap was put in there. Ozone depletion, what a farce, even NASA quietly backed off this issue.

One thing for sure, repairing an AC system is no longer a five minute job.

To check a clutch coil, I hook up a volt/ammeter power supply directly to the clutch coil, typically should show 3-4 amps at 14.5V, but leave it on for awhile, as the coil heats up, that current should go down. If it goes up, your coil windings are shorting out. Also the clutch should engage, with a variable power supply, can find what voltage the clutch will engage at, I like 10.5 volts as a safety margin.
I always enjoy reading your Tech info come Geopolitic A-Z of US government departments rant mate, Cheers from Australia (now where's that gif of Michael Jackson eating pop corn?)
 
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