2001 to 2003 prius air conditioning adjustment of the clutch

Thanks for the post. I recently replaced my 2001 Prius, with another 2001 Prius. In the "new" Prius the AC will only work for a few minutes and then shut off with the blinking light. It shuts off even quicker when I use MAX. I tried to run the AC code. It seems to blink at a constant rate, instead of the two pause two (22). I checked the refrigerant pressure. It is 110 psi when off, and 35 psi when running. Seems fine, and cools well when running.
I plan on trying your repair this weekend. I hope it works.

 

If you've got a scale you can set your refill can on, you've really got all you need to go the last step and make sure you've charged the right amount: you're watching for the sight-glass bubbles to just disappear, then adding 100 grams more, plus or minus 50 - the details are here, be sure the engine RPM and other conditions match. Don't tip that can!

When working on the clutch, you might find one, two, or three shims behind the pressure plate: the shim kit comes with three, but they're different thicknesses (0.1, 0.3, and 0.5 mm) and you put in whatever combination will give you about half a mm of pressure-plate travel. If that only took one or two shims last time and the others weren't saved, you can get a new set of all three for about $1.21 at the dealer. The shims aren't marked for thickness; if you've got the whole set in front of you and you know they're different, you can manage to tell which is which by look/feel, but if you don't know they're different or you don't have all three, measuring is the best way to tell which you've got.

(You could even get a surprise - what came out of mine was some random washer that must have been put in by somebody a previous owner knew, and was almost double the maximum thickness you'd get by using all the shims!)

If you measure the total thickness of the shims you took out, add half a millimeter (what the pressure-plate travel is supposed to be), and subtract what the pressure-plate travel really was before you took it apart, the result is the shim thickness you should aim for when you put it back together. Just look for what combination of the 0.1, 0.3, and 0.5 shims will add up to that thickness (within 0.15 mm either side is ok). When I did mine I had two possible combinations within 0.15 mm, one on the tight side and one on the loose, and ended up going with the loose one because the tighter one did drag just slightly.

For measuring the pressure-plate travel, one way is to use a feeler gauge between the plate and pulley faces while they're disengaged, and another is to clamp a dial gauge to some solid engine part with the plunger resting square on the pressure plate, then give 12 volts to the clutch and watch the dial for how far the plate moves.

When the clutch is new, either way works well. The feeler gauge, not so much once the clutch is worn, because they always seem to wear in a strange pattern of rings (mesas and canyons). The two faces still fit perfectly (after all, they ground each other into that shape), and a dial indicator will still show you the distance the plate pulls in, but trying to stick a feeler in between those mesas and canyons may give you a weird reading.

-Chap

 

Hi Roy,

Just so there's no confusion, ONE HALF MILLIMETER is the specified travel. 0.5mm ± 0.15mm is the desirable range according to the manual.

Yes, when I got around to mine it was traveling 1.34 mm (more than double the spec, on the way to triple), and at that distance the magnetic field could barely budge it (in ON only, where the voltage was just 12 V from the aux battery. At 13.8 V from the converter with the car running, it still pulled in most of the time).

There I was with my dial gauge set up on the plate, in my hand an old remote-starter button that I had clipped into pins 3 and 5 of the CLR MG relay socket so I could easily click the clutch on and off, and I would push the button and see the pressure plate sort of lean in on one side. So I'd reach up and nudge it with a finger and SNAP! it pulled in, and that's how I got the before reading.

In my case all I had to do was throw out the screwy oversized washer that was in there, and put in two of the proper shims. I still don't understand what a 1.5 mm washer was doing in there - was that just some previous-owner weirdness on my car, or has anybody else pulled out one of those?

I think for my part if it ever came to not being able to meet spec even with no shims, I'd just go ahead and buy a clutch at that point. I'd assume by that time the old one could have been re-shimmed two or three times, the car's probably got 400,000 miles, and maybe the bearing that's built into the clutch pulley wouldn't owe me much beyond that.

-Chap

 

Worked on it this weekend. With just turning the wheel to the right, and removing the shield, gave plenty of room to work. I used a cheap old oil filter wrench to hold the pulley while removing the bolt. Looks like the gap was about 1.2 mm. It had a 1.4 mm washer inside. I ordered the shim kit. In the mean time I but a .7 mm nylon washer in. Seems to have solved the problem

 

I had the same problem, A/C would work initially and it seemed like on the hottest days it would stop working after a few minutes and the light would flash. Sometimes I could get it to work by turning off the A/C and turning it back on again but would work for shorter and shorter times. Eventually it basically didn't work. Dealer suggested replacing compressor for $1K but thanks to you guys I printed out this discussion thread, showed it to my mechanic, and he completely fixed my A/C, so I really appreciate you guys posting this info. Hope it helps others too.

 

OIL FILTER WRENCH TO HOLD THE AC CLUTCH! this is why I love Priuschat. Thanks Rob you just gave me the courage to try and fix my blinking AC.

 

just had the same thing with my 01 prius.. Thanks for the post ..Took about 20 mins and seems to be working great now..

 

I used my 1/2 inch impact gun with an 10 mm socket to remove center bolt. Just a quick short pull of trigger, bolt broke free.

 

Can someone post the part number for the shim kit?
BTW, the first step in diagnosing 'blinking' AC difficulties is to replace the drive belt. After a few years, the belt gets dry and much more prone to slipping. Second step is disassemble and clean. I have had good luck when, after disassembling the magnetic clutch assembly, using a dremel tool plus a bronze brush and clean all the iron oxide dust off both surfaces of the clutch faces. This seems to be a major failure mode in the northeast/mid-central states where lots of salt gets used in winter. Of course, the thickness of the shim and the proper setting of the gap is important. The torque setting of the magnetic clutch center bolt is critical. I once accidentally over-tightened that nut, and the clutch could not disengage... made for a very chilly ride.

Cheers, all.

 

Inspect the belt and its tension as one diagnosis step, sure ... replace it unconditionally as the first step? I don't know ... it's both more expensive and more work to do than the clutch adjustment ($1 shim kit, one bolt, ten minutes).

I don't know that I'd fuss with bronze-brushing the clutch or anything like that, except maybe as the last step if I knew the belt was good, and I knew (from a dial indicator) I had properly adjusted the gap to 0.5 ± 0.15mm and it was still, for some reason, slipping (which is a situation I don't actually expect anyone ever to see).

-Chap

 

Thanks for posting the shim part number. Toyota calls it a "Gasket kit, overhaul".

Well.... if I'm going to go through the effort to lift the car, remove the front wheel and the inner splash shield, and there are 3 possible failure modes which can be addressed (slipping belt, worn clutch shim, buildup of friction-reducing debris on clutch face), I'm going to go in and clean the clutch face, replace the belt, and finally set the clutch gap in one operation. Parts cost is minimal (belt is $10, shim kit $2, dremel is already paid for), so the biggest "cost" is my time in getting to the clutch.

In this case, I was surprised that a two year old belt was slipping (may have been old stock when I replaced it; it did not appear cracked, but wasn't very grippy). So while I am there, I do all the remedy actions that I know about.

Probably the trickiest bit is getting belt tension correct - overtension will stress the water pump bearings, and replacing the water pump if painful (I did that once). Getting the belt tensioner to adjust smoothly is a bit of a chore; I've needed to loosen the tensioner bolt with a hammer on a socket plus extender to initially release tension on the belt, after providing some lubrication to the tensioner slide faces.

I have a hard time figuring out what kind of wear would cause the gap to change enough to fall out of operation and show the AC_ClutchSlipBlinkSignal, such that ONLY resetting the gap restores proper non-slip operation. Either the clutch faces wear (which would either [a] make the gap larger, allow slip; remedy with a smaller shim, OR wear/debris build-up lubricates the clutch face interface, allows faces to slip, thus normal hold-in force of the clutch is insufficient to couple shaft to the drive belt), OR the spacer wears (gets thinner), for which I can't figure out a mechanism which would allow the clutch to slip as the clutch gap gets smaller.

On the 4 or so Gen1 Prii that I've looked at (mostly driven in the NorthEast; maybe that makes my fleet a special case), replacing the belt or cleaning the clutch faces has eliminated the blinking AC problem. All the clutches I've seen had a buildup of rusty powder on both clutch faces. Until this last instance, which I attribute (mostly) to a dried-out new old stock drive belt that I used to replace a VERY cracked and dried belt a couple years ago. I could never see any signs of wear of any of the spacers I removed.

So thanks to all who have watched and commented in this thread; it's been very helpful.

I wish many years of cool, unblinking AC performance in your Gen1 Prius to you all.

 

Just wanted to add feedback and say THANK YOU. Got myself a solid 2001 Prius with 123k miles. Clean no rust. Chicago car. Kept in garage condition most of life. Hybrid battery failed so scored the car for $700 cash. Towed home and sat for 9 months (a baby could have been born). Harsh winter came and gone. Finally had the time to get out and pull battery out and replace 2 dead cells, balance, and presto. Prius runs. 51MPG in last 250 miles.

Only issue is... A.C blinking lights. Googled. Found trusty old Prius chat. Seemed easy enough on this forum post. Jacked up passenger side. Removed wheel using 21 metric socket and impact. Removed two more 10 metric screws holding plastic cover. And found the clutch with the plate and removed using impact again and 10 metric. Pulled off easy, and one washer came out. Rather thick it seemed. Not 3 or 2 just 1 washer. The axle or spinning center of clutch had a washer looking end but it would not come off so figured it may have been corroded on over time. Regardless to say, A.C works! Recharged using hybrid specific.