Air conditioner clutch shim removal

[jsheahawk]

If you have problems with your A/C clutch disengaging when the weather gets hot, removing the shim behind the clutch plate might solve your issue. This is an easy one, and the toughest part for me was getting the magnet wires back probed. All told, this fix took me less time than it took the wife to get back from the grocery store.

This is all you'll need to do this job:
14mm socket and accompanying ratchet
Two wires with alligator clips on both ends
A couple T-pins
Pick set
Flat blade screwdriver



The compressor is straight down from this arrow. It's on the bottom below the alternator. If you don't know where it is, you probably shouldn't be attempting this.



Throw the 14mm socket on the center nut of the compressor clutch, and you'll find out pretty quickly that it just spins because the clutch isn't engaged. You could buy a special tool for this, but the clutch will do all the work for us if it were only engaged. Luckily electromagnets aren't exactly complex things; they just need power!

Backprobe those two wires that come out of the right side of the compressor. Red is positive, black is negative. Put the socket on the nut now because it'll be harder to get on there with the magnet engaged. Connect the wires straight to the battery, and you'll hear a satisfying click of the clutch engaging. Jumping the relay is probably a more elegant solution. It's #44 under the hood. Thanks, Moose. With the clutch engaged, getting that nut off is pretty easy. You may need to grab one of the pulleys to keep the whole belt from spinning. Be careful not to let the pins/clips touch while you're digging around down there. Ask me how I know.



With the nut off, use the flat blade screwdriver to gently pry the clutch plate off of the clutch. It'll look like this when you're done. On that shaft is a thin washer. Use a pick to get it off of there. Mine was stubborn. Yours may have more than one shim, but mine only had one.


Here are a couple pictures of the clutch plate. That's the shim I took out sitting on the plate.



Once you have the shim off, slide the plate back onto the shaft (a bit of grease wouldn't hurt), put the nut on finger tight, re-engage the clutch if you need to, and tighten the nut down. Test and celebrate!

 

[Matt]

Thanks for the write up. Mine is great when you start but after maybe 20 minutes the clutch disengages and won't come back on unless I hit it with a screwdriver.

I was going to replace the low pressure switch but I think I'll try the shim first and see what happens.

Thanks again.

 

[steveO]

Removing the shim, if it works, is only a temporary fix. The clutch surfaces will grind as you can see in the photos (center area) and make engagment less reliable. That grinding will eventually scar the entire clutch surface. Is the engagment positive or does it grind and slip to full engagement.
Check the condition of the hub bearing with the belt off, it may be the problem. Having fixed this issue a couple of times ...the bearing was the main cause. If you replace the bearing you can save the cluch surfaces otherwise the clutch will end up needing replacement .

The low pressure switch is easy to access but if you always loose the clutch engagement after it runs for 20 min i doubt that is the problem. Inspect the connector on the switch and reseat it.

 

[jsheahawk]

If it lasts a few years, I figure I got my money out of the repair.

It would be nice if they sold the clutch separate from the compressor.

 

[Mooseman]

When I did it on the '02, it lasted 6 years. YMMV.

BTW, a much easier way to engage the clutch would be to jump the relay.

Added this to the FAQ.

 

[jsheahawk]

When I did it on the '02, it lasted 6 years. YMMV.

Fingers crossed.

BTW, a much easier way to engage the clutch would be to jump the relay.

That would have been way easier. I updated the OP.

Added this to the FAQ.

I've hit the big time now!

 

[$ Khalid ! 9130]

Great write up @jsheahawk. And i gotta comment on that sick engine bay. Any links to how you got it looking like that.

Back on took what exactly were the symptoms you were experiencing with the air conditioning?

Thanks

 

[jsheahawk]

Great write up @jsheahawk. And i gotta comment on that sick engine bay. Any links to how you got it looking like that.

Back on took what exactly were the symptoms you were experiencing with the air conditioning?

Thanks

I may have stolen that picture from the internet. To the person who owns that engine bay: Thanks and it's lovely.

I was having the common issue of the AC working perfectly for a while then suddenly quitting while driving. It would also not cool at idle. I'm assuming that was because the clutch was slipping.

Here's a good video from realfixesrealfast on how the AC clutch works.

 

[$ Khalid ! 9130]

I may have stolen that picture from the internet. To the person who owns that engine bay: Thanks and it's lovely.

I was having the common issue of the AC working perfectly for a while then suddenly quitting while driving. It would also not cool at idle. I'm assuming that was because the clutch was slipping.

Here's a good video from realfixesrealfast on how the AC clutch works.

Ah I see it looks gorgeous though. I have a friend of mine who also owns a trailblazer and is experiencing similar problems. Thought I'd ask for him. Thanks

 

[05TuckerTB]

Hey Guys,
What was the final outcome on this?
My AC doesn't work when it's hot(like most of the year here in Hotlanta). Clutch seems to always be engaged and the AC works great if I keep moving, but that doesn't happen too often in this town!
System appears to be fully charged, but that's based on one of those auto parts store recharging kits!
Thanks,
Frank

 

[Mooseman]

Sounds more like your fan clutch is not working.
How to test the electro-viscous fan clutch

 

[TJBaker57]

Clutch seems to always be engaged

Does the clutch look to be engaged when the A/C has stopped working?

 

[gpking]

Clutch seems to always be engaged and the AC works great if I keep moving, but that doesn't happen too often in this town!

Did you remove the shim? When I tried that my clutch was effectively engaged at all times. It just slipped badly above 1500 rpm when "off" and made a horrendous burning smell. I'm probably the only one who has had that happen lol.

 

[05TuckerTB]

Sounds more like your fan clutch is not working.
How to test the electro-viscous fan clutch

Hey Mooseman, yeah.....I watched that video with the grabbing the fan with the rag(yikes!)
I don't know...….I'm a little afraid of that test

 

[05TuckerTB]

Does the clutch look to be engaged when the A/C has stopped working?

TJBaker57,
That's a good question! I need to check that in the morning.
From what I've seen in the videos, I suspect(at this point) that it could be the pressure switch/valve on/in the compressor, but it's a guess.

Whilest I have your attentions, I got a couple of questions about the diagram attached to this post:
I understand what the A/C Low Pressure Switch does. Keeps the compressor from engaging if there is not enough Freon in the system. That one is pretty straightforward. However....
1) A/C Refrig Pressure Sensor - does this actually measure amount of Freon in system?
2) A/C Comp Temp Switch - Cuts off comp if temp gets too high?
3) HVAC Control Module - Tells PCM that AC is working/not working?

Thanks to all that have taken the time to reply. If I wait a couple of more months, I won;t need to deal with this problem until next year(lol)!

 

[05TuckerTB]

Did you remove the shim? When I tried that my clutch was effectively engaged at all times. It just slipped badly above 1500 rpm when "off" and made a horrendous burning smell. I'm probably the only one who has had that happen lol.

GPKing,
Have not removed shim yet. I'm going to check to see if clutch disengages when AC is turned off. That will be checked in the morning.

Thanks again for all ya'lls replies!

 

[TJBaker57]

So,, when you can, check to see if the clutch is disengaged when it you want it not to be. That is to say you need the A/C on but now you've gotten stuck in traffic or it's just damned hot and the A/C quit on you.

 

[05TuckerTB]

Sounds more like your fan clutch is not working.
How to test the electro-viscous fan clutch

Mooseman, HOLY CRAP BATMAN!!!!! I just looked up the price of that puppy. OMG
My wallet is crying and I haven't even ordered it. That fan clutch test is looking better already so that I can be sure before forking over that kind of doh-rey-me!
Any suggestions regarding aftermarket replacements? The GM part is $329, but that's on the GMDirect site. RockAuto has the Delco part @ $227. There's also Dorman @ $117 and GMB @ $127
I guess I'm re-reading that test link you posted :-(
Feedback welcome!
THank you,
Frank

 

[TJBaker57]

1) A/C Refrig Pressure Sensor - does this actually measure amount of Freon in system?
2) A/C Comp Temp Switch - Cuts off comp if temp gets too high?
3) HVAC Control Module - Tells PCM that AC is working/not working?

1) No it does not measure the amount of refrigerant. It measures the pressure of the high pressure side of the compressor, the output of hot gas on its way to the condenser coil. The computer uses this information, and quite possibly other data as well, to decide how much the electro-viscous fan should run. I believe the PCM also shuts off the compressor if this pressure goes too high.

2) Correct. Compressors are mainly cooled by the cold refrigerant (in vapor form) returning from the system. If the refrigerant charge is incorrect , under some circumstances the compressor could get too hot.

3) The PCM enables the A/C relay by grounding the DK GRN/WHT wire. The A/C relay provides positive battery power to the compressor clutch which is already grounded at the other end. The LT GRN wire from the clutch assembly to the HVAC module tells the HVAC Module that the clutch is enabled, and although I am not certain of this, I think the HVAC module can tell if the clutch is engaged or not. Again, not sure of that last bit.

 

[TJBaker57]

HOLY CRAP BATMAN!!!!! I just looked up the price of that puppy. OMG

I grabbed one at a U-pull&pay yard for $20. The connector needed a little tweaking but it works now. The bearings on my original were on their way out.

 

[Mooseman]

Hey Mooseman, yeah.....I watched that video with the grabbing the fan with the rag(yikes!)
I don't know...….I'm a little afraid of that test

You can also wear heavy work gloves if you want. It's really not that bad... to lose a finger

You already grabbed a used one and seems to work now but for future reference, Hayden is the best balance in price and quality. Dorman is junk and other knockoffs are too unknown to waste money on.

 

[05TuckerTB]

So,, when you can, check to see if the clutch is disengaged when it you want it not to be. That is to say you need the A/C on but now you've gotten stuck in traffic or it's just damned hot and the A/C quit on you.

Huh??????? "clutch is disengaged when it you want it not to be" Can you please translate that?
If I shut off the AC, the clutch should disengage......right? Is that what you said?(lol)

 

[05TuckerTB]

You can also wear heavy work gloves if you want. It's really not that bad... to lose a finger

You already grabbed a used one and seems to work now but for future reference, Hayden is the best balance in price and quality. Dorman is junk and other knockoffs are too unknown to waste money on.

I didn't see Hayden on Rockauto. Who is GMB? I figured that the Dorman was junk based on some other parts that folks have posted about using Dorman.

And I like having 10 fingers!

 

[Matt]

I didn't see Hayden on Rockauto.

It's the 4th one down. https://www.rockauto.com/en/catalog...31160,cooling+system,radiator+fan+clutch,6812

But, you might want to get the 2851 for an 08 and have the code it'll throw tuned out. https://www.rockauto.com/en/catalog...41133,cooling+system,radiator+fan+clutch,6812

 

[TJBaker57]

Huh??????? "clutch is disengaged when it you want it not to be" Can you please translate that?

I am trying to say that you should check to see if the clutch is engaged when the A/C fails. You said it quits working when you aren't moving and/or it is very hot out. When you have the A/C on and it is not working right, check to see if the clutch is engaged.

 

[Mooseman]

I checked them out on RA and there isn't much of a price difference anymore between the EV and thermal clutches. The only real difference now is reliability. The EV used to be almost double the price.

 

[TJBaker57]

I went the pull & pay way because I am new to Pull&Pay and it still kind of fun to me. I figured it was worth a try, my existing one had bad bearings.

 

[05TuckerTB]

I didn't see Hayden on Rockauto. Who is GMB? I figured that the Dorman was junk based on some other parts that folks have posted about using Dorman.

And I like having 10 fingers!

Looks like Hayden doesn't sell their stuff thru any online sites. All I could find were brick and mortar stores in the upper Midwest...….
I

It's the 4th one down. https://www.rockauto.com/en/catalog...31160,cooling+system,radiator+fan+clutch,6812

But, you might want to get the 2851 for an 08 and have the code it'll throw tuned out. https://www.rockauto.com/en/catalog...41133,cooling+system,radiator+fan+clutch,6812

Hey Matt,
Thanks! I swear it wasn't there last night! It's the OEM replacement and it has the recomendations of this esteem group

 

[05TuckerTB]

I am trying to say that you should check to see if the clutch is engaged when the A/C fails. You said it quits working when you aren't moving and/or it is very hot out. When you have the A/C on and it is not working right, check to see if the clutch is engaged.

Hey TJ, I got it now! Yes, the clutch is still engaged when it "quits" working. It stops working in the sense that it no longer blows cold air. It's not as hot as ambient, but it is also not cold.
Would Voltage regulator flakiness cause any troubles with AC?
There's a sporadic voltage fluctuation that reared it's head today. I gotta post that one in the appropriate area.
Thank you again for you replies and help.

 

[Joe_67]

I am right in the middle of this shim pulling exercise (though in the long run I'll likely end up ordering that clutch kit that mooseman found (https://gmtnation.com/forums/threads/a-c-clutch-kit-from-aliexpress.23062/) - many thanks for that...)

My worry is that my air gap was somewhere around .033-.034 and I only have one shim in there which is .027. So I figure if I pull that I end up with an air gap at only .006 and I think the minimum is supposed to be .02. (Gap measures with feeler gauges and shim measure from digital caliper). I feel like I'll end up with the constant engagement. Thoughts?

A couple of side-notes:
- thanks to jsheahawk for posting this.
- I'm in an '02 Envoy SLT and I think it's harder than what some others are in as there is very little clearance between the cooling fan and the front of the compressor. It's really hard to even get my hands in there.
- I did manage to wiggle & jiggle an air ratchet down there which broke the nut loose without needing to engage the compressor. Might work for others.

 

[Joe_67]

Ok - forget my post immediately above (#30). B/c I was right in the middle of it and needed to do ... something. (Guess I posted on the off chance that it's Saturday and I might get lucky with the right person or two online at the time).

I did think about sanding on the existing shim, and tried for a bit. It works, but of course would take forever. So I did the garage hunt and came up with a roll of metal strapping tape. It was in the right thickness range and is easy to work with. I screwed a pc down to a block of wood, put it on the drill press and enlarged a hole. (I'm sure the shaft size is in mm, I found a 15/32" to be a hair over and 29/64 a hair under - I went a hair over, of course, but the job of this thing is not complicated).

Anyway, a little snip-snip to get it about right, some de-burring, and a little pound flat with a hammer and I put it all back together. My gap is now at about .025 which is right in the center so I'm good with that.

All I can say now is that I didn't break anything any worse than it was already. I started up and the compressor kicked on-off as commanded. My problem was only when everything got hot though so I won't know if it helped anything until I take a drive in it. (Right now not wasting gas just to check something I can check next time I go out!)

 

[Mooseman]

I think as long as it doesn't constantly rub on the clutch, the gap can be as small as a cat's hair. And if it does slightly rub, it will likely stop as soon as it is engaged a few time to shave the clutch off a bit or to get rid of the surface rust.

 

[Joe_67]

I think as long as it doesn't constantly rub on the clutch, the gap can be as small as a cat's hair. And if it does slightly rub, it will likely stop as soon as it is engaged a few time to shave the clutch off a bit or to get rid of the surface rust.

Thank you! I think I got scared off by gpking's experience (post #13 above), largely b/c I'll probably do the clutch and don't want to wreck anything in the meantime.

 

[Mektek]

As long as you can freely rotate the front of the clutch by hand then the clearance is OK. If it rubs on the pulley it needs a thicker shim.