Air conditioner clutch shim removal

jsheahawk

Well-Known Member
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

IMG_20170723_134131.jpg image_16048.jpg800-041.JPG

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. :biggrin:
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2005-gmc-envoy-42-engine-BDgNBSz.jpg

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!
DSC04407 (1).JPG
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.
IMG_20170723_133104.jpg
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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.
IMG_20170723_133047.jpg

Here are a couple pictures of the clutch plate. That's the shim I took out sitting on the plate.
IMG_20170723_133026.jpg
IMG_20170723_133011.jpg

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!
 

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Matt

Silver Supporter
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

Well-Known Member
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.
 
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OP
OP
jsheahawk

jsheahawk

Well-Known Member
If it lasts a few years, I figure I got my money out of the repair. :2thumbsup:

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

Mooseman

Moderator
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.
 
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jsheahawk

jsheahawk

Well-Known Member
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

Well-Known Member
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 :2thumbsup:
 

05TuckerTB

Member
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

Moderator

gpking

Well-Known Member
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

Member
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)!
 

Attachments

05TuckerTB

Member
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

Well-Known Member
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

Member
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:yikes:
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

Well-Known Member
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.
 

Mooseman

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

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

Member
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

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

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

Silver Supporter

TJBaker57

Well-Known Member
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

Moderator
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

Well-Known Member
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

Member
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
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:dunce:
 

05TuckerTB

Member
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.
 

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