A/C Clutch Diagnosis and Replacement

well done, we need more like this for the DIY and customers to be better informed. Keep up the good work.

 

Wow, what a great info share/write up. Especially for the Gen I guys (like me). I've done a post like this b4 so I can appreciate how much time and effort went into it. I've said it b4 n I'll say it again, the Prius is better supported online than the Ford Mustang. The Mustang has been dethroned!!!!!!!

Thanks Station2Station

 

What a great write-up, Station2Station!

It deserves the final polishing touch with the last few details you'll find in the service manual (either paperbound or on techinfo.toyota.com):

• You already recommended buying the C-clips and shims (items 6,7,9) just in case of breakage, but more than that, Toyota calls the C-clips nonreusable, so to be fully by-the-book you would always install the new ones.
• If the pressure plate is stubborn coming off, there's a special tool for it. From the diagram it looks like the center of the plate is threaded (for a larger diameter bolt than the one holding it to the shaft), so if the pressure plate won't pull off easily, you can just thread the correct-size larger bolt through and turn clockwise to drive the pressure plate off.
• If you look at the inner edge of the C-clips, both are beveled on one side. On installation, the beveled side has to be facing away from the compressor (out toward the wheel well). In other words, the clip's flat side always goes against the part (magnet or pulley) the clip is meant to hold in place.
• The "German torque spec gudentyte" is 13.2 newton-meters (9 or 10 foot-pounds), no more. That's not super-tight; it would be easy to overdo it.
• You really want to select the shim or shims that give you a pressure plate clearance of half a mm (plus or minus 0.15 mm). You don't want the clutch dragging when disengaged, but you don't want it slipping when engaged either (after all, that's why we're doing all this!). The idea is to clamp a dial gauge to a solid fixed point on the engine or compressor, with the point resting on the outer face of the pressure plate. Then apply 12 volts to the magnet coil. You want the dial gauge reading to change by 0.5 mm ideally. If the change is < 0.35 mm go with more shim, if > 0.65 mm then less shim.
• If you have a belt tension gauge then you want 110 pounds (plus or minus 11) if the belt is brand new. 67 pounds (plus or minus 10) if it's got more than 5 minutes of run time.
• Torque for that 14 mm tensioner pulley center lock nut is 40 newton-meters (30 foot-pounds) once you've got the belt tension right.

Those are the only extra points I know of. Thanks for a really detailed write-up!

-Chap

 

Well done, waste around $500 for used compressor 2 years ago when I could just do that

 

I finally got a couple code 22s a week or so ago, doing 70 uphill on I-65 in Tennessee. Last night I put a dial indicator on the pressure plate and measured the travel when energizing the clutch magnet. (I didn't want to fuss with the connector down at the compressor so I pulled the CLR MG relay and worked the clutch with a jumper between pins 3 and 5 of the relay socket with the ignition on.)

The spec is 0.5mm ± 0.15mm. Mine traveled 1.34mm. Oops. At that distance the plate isn't even much within the field of the magnet, and at the lower battery voltage with the car on but not ready, it didn't reliably pull in without a little nudge, or it would pull in on one side and not the other. (The 13.8 volts when the system's ready probably makes a difference - I haven't had any slipping trouble except those two times in TN.)

After removing the bolt, the plate slipped easily off, no puller required. Behind it was a single spacer washer 1.5mm thick. I don't even know where that came from! According to the manual the ones in the shim kit should be 0.1, 0.3, 0.5 if I remember right. Could somebody have had this off once before and just slipped in some old washer from the junk drawer?

I'll see what comes in my shim kit when it arrives at the dealer. A 0.1 plus a 0.5 ought to get my clearance within spec.

-Chap

 

Great work!!!!

 

Hehe. They arrived today. They are very thin, and they might look the same size, but just as the manual says, they're 0.1, 0.3, and 0.5 mm. They have no markings, so you need to have a sharp eye, or cheat.


I had calculated that the 0.5 plus the 0.1 would give me a travel of 0.44, comfortably in spec just a shade on the tight side. That turned out to drag just a tiny bit; the plate would sort of drift around lazily with the engine running when it should be disengaged. I swapped out the 0.1 for the 0.3 to get a 0.64 mm travel just barely within spec on the loose side. That's behaving perfectly. Being on the loose side already it won't stay in spec for long, but I'm sure after it has worn a bit that way, I'll be able to swap the 0.3 back out for the 0.1 and it'll be fine.

Cost of repair parts: shim kit $1.21.

If dealing only with the clutch plate and shims, no need to remove the wheel or disturb the belt, pulley, idler, coolant bottle, etc. Just steer the wheels to the right, drop the right side plastic under cover, loosen the clutch center bolt, slip the plate off, change the shims and reassemble. Piece of cake.

-Chap

 

Excellent thread, my vote for a sticky.

Just an observation: I have just recently replaced the a/c clutch on my '02, and whilst looking at the corpse of the old clutch, I decided... that maybe the "wear marks" weren't really wear marks, they looked too regular. So I took my trusty dremel tool and a bronze brush and spent 10 minutes getting rid of all the rust powder. Wipe with a cloth containing some brake solvent, and the "old" part looks like the structure was machined. So, since the procedure was so easy... I put the old part back in place of the new one, and viola, the a/c works like a champ, no blinking light.

Anyone want to buy a gently used almost new a/c clutch?

I now suspect that the REAL culprit is the buildup of rust debris between the faces of the clutch, causing slippage under load.

So the low budget procedure (which only requires partial disassembly of the clutch) is to replace the serpentine belt (good practice, if it looks at all worn) and then carefully clean the clutch faces with bronze wire brush/dremel tool plus cleaner, and reassemble. Excellent writeup, Station2station.

By the way, the part number for the '03 Prius a/c clutch is different than '01/02, is twice the price, and uses a bearing half the thickness of the '01/02, so an '01/02 clutch can't be used on an '03.

I would add that a single drop of LocTite might be recommended for the one bolt holding the outer clutch plate, Gudentyte is a nice spec but things would be ugly if the screw later walked out.

 

Station2Station should be a tech writer for auto repair.

 

Air conditioners with magnetic clutches have been around long enough there isn't much mystery left about the real culprit. The faces wear, and the distance the plate has to pull in to engage increases beyond the spec. There are pretty much always shims you can change to put it back in spec, and you're done, for a hundred thousand more miles.

Measure the travel, choose the right new shim(s) to bring it back to (for this compressor) 0.5 ±0.15 mm, put the bolt back in, and you won't be looking at it again for a good long time. The shim kit is a buck and the job is ten minutes.

If you're having symptoms, you'll probably measure your current travel to be out at twice the spec or more. Mine was 1.34 mm when my symptoms showed up (at well over 200,000 miles). That far out of spec, if you don't fix the travel, anything else you do (dremeling the surface, spreading with peanut butter, whatever) might make a difference for a while—who am I to say it couldn't?—but you'll be kind of ignoring the real culprit.

Toyota doesn't advocate loctite for the center bolt, but (as covered already in this thread) they do give a correct torque for it, not just "gudentyte". Shouldn't be any trouble if that's followed.

-Chap

 

Please sticky this thread...

 

If the A/C light is blinking and can be relit by turning it off and on then it is for sure he shims that need to be thinner. I'm sure.

 

I did this repair, this afternoon, on my '01. This thread was very helpful - thanks!

A few notes:

The assembly will want to spin when you go to remove that center 10mm bolt. I tried engaging the clutch with a jumper wire, and holding the belt, but that didn't work - the pulley slipped on the belt when I used a ratchet on the bolt. The Black and Teal Book of Truth shows a special tool to hold the clutch plate, and Autozone rents one that has three radially-adjustable pins, but I couldn't totally convince myself that that tool would work on my clutch plate - I think the pins are supposed to go into holes on the plate, which I didn't have. I spent some more time Googling, and found this nugget in a repair procedure for another car (a 2006 Ram 2500 pickup, of all things, that also used a Denso compressor):

Use a strap-type oil filter wrench to hold the clutch plate.

I had a wrench like that lurking in my toolbox, last used on my old Ford, 12+ years ago. It was big enough to fit the common Motorcraft FL-1A oil filter. I put it over the clutch plate, and it held just fine while I loosened the bolt. I measured the plate and it is about 94 mm or 3.7" diameter, if you're shopping for a wrench.

I'm about 98% sure the clutch plate has never been off of mine, and I found the same single thick washer that Chap did. Mine was about 1.3 mm thick. Using all three of the new shims to get 0.9 mm put me on the tight side of the acceptable range.

(I don't know, but I suspect that maybe Denso designs the clutch with way more pull than it will ever need, and then puts that large washer in there to keep it from dragging or locking up when things are new. When things are not new, they supply thinner shims as a replacement.)

The back of the clutch plate and the face of the clutch were rusty on mine. I don't think it was hurting anything, but I did wire-brush the rust and wipe them both off.

When measuring the movement, jumping the pins at the CLR MG relay socket, with the key on, is IMHO the way to go. It's a lot easier to reach than the connector at the compressor. The relay socket is tenacious; it helps to use a wide, flat thing (KEY OFF) to pry up between the socket and the relay, to start to remove it. Once it's several mm up, you can grab the relay and pull it out by hand. (The relay has a couple of pips on the outside of the casing, and I bet there's a tool you can get at the Super Denso Store in Akihabara that uses those pips to remove it, but I just used a screwdriver. ) The pins you want to jump are the ones that the copper-colored prongs on the relay went into; I used a short piece of wire with 1/4" push-ons crimped onto each end.

The part number for the shims is still 88335-14020, "GASKET KIT-OVERHAUL". No, I don't know why they call it a gasket kit, either. I paid $1.34 plus tax in spring 2019 from my favorite local dealer.

The Hazard Fraught Harbor Freight Tools dial indicator (63521, currently $17) and magnetic base (63663, $13) worked OK for me for this job. The magnetic base isn't great at sticking to steel things, but in this case, I just set it on the driveway under the car. If you do this, don't get in or out of the car, or lean on the car, until you're done measuring, because the suspension movement will affect the reading.

(And we know about going in with one 20% off coupon, buying the first thing, taking it out to the car, and going back in with another 20% off coupon for the second thing, right? Right. Good.)

I ran the engine and took it for a short drive and the A/C seems to be working normally. Mine was not failing all the time, though; it'd only quit when I was blowing down the Interstate on a really hot day, or sometimes when I was accelerating on an uphill on-ramp or something. So it will take me a little while to verify it, but I have confidence.

 

Glad it worked for you.

One more cheap tool that can make the job more pleasant is an old-fashioned remote start button. They used to sell these things, probably still do, just a big pushbutton on several feet of wire with little clamp terminals at the ends. You could clip it over the starter solenoid terminals (back when your car had a starter solenoid and a starter) and use it to check starting while you watch under the hood.

In this case, you can just clip the leads to the CLR MG relay socket terminals and take the button around with you to click the A/C clutch in and out while you watch.

People who have an impact wrench can use that for loosening the center bolt. It is a very small bolt and certainly doesn't need a power tool for either loosening or tightening, but light application of an impact wrench in the loosen direction can knock it loose without spinning the clutch, just from the element of surprise.