Intermittent AC - clutch pulley jerking/sparking

04 Jetta, 224k miles. I'm the second owner, purchased at 36k or so. I do not believe I've ever needed to recharge the system, but I have replaced the clutch coil by itself once and the whole pulley/coil assembly when the bearing failed and toasted the coil. Both fans were new last year and work perfectly.

AC has always been ice cold until yesterday (95F ambient, engine just over 190). I jumped on the throttle a bit and the AC cut out but didn't come back on. I could smell a burning rubber smell so I shut the ACoff and dropped the car off at home and took another. Later, the AC worked great.

I drove it 45 minutes this morning with great AC (over 90F again). On the way home, it cut out and I could smell what I would describe as overheating brakes. I checked and the AC clutch pulley was slowly jerking with small sparks. I drove home with it off but picked up my AC tools on the way home.

Of course when I got home to test, the AC worked perfect. Both fans are new, charge (low side) read 140 off, 40ish running. Beautiful cold air.

When I replaced the pulley, I fitted the faceplate using the original shims (this was just enough to let it freewheel without dragging). Could I need to remove one or is the compressor locking up? No belt squeal, no abnormal engine load, etc.

Experienced the same thing today except I didn't see any sparks. Perhaps there were sparks but I didn't see them. I did smell burned clutch material, though. A/C fan works fine. It's just not engaging!!! Makes me think the coil is toast or it's not getting power. Fuses are fine. I'm thinking it could be the coil and/or the clutch assy. It'll have to wait until this weekend before I can get under the car to surmise and decide what to do. I hope the compressor is ok.

Mike in West MI

I've never seen a coil that was intermittent, but it is an aftermarket part (polar air, I believe?). It's a pretty simple electromagnet - coil is energized and it attracts the end plate, pulling it to make contact with the pulley. I expect some slippage as it first engages, but it seems like mine is slipping more when hot.

Hopefully someone else has had one partially engage.

I also have had this happen, it started about 3 days ago. I had the burning rubber/ electrical smell with squealing when first started for about 20 seconds then be fine.
I had just ordered today a new clutch pulley for Wednesday delivery, went for pizza , picked up pizza and car would not turn over, sounded like a dead battery.
Needed to cut accessory belt off and car fired right up. Drove the car home the 7 miles with no power steering and battery light on.

Word of advice if it's making noise don't drive it, just my .02

Yeah a friend of mine got a Golf that allegedly had a locked up engine.

Well, the ENGINE wasn't locked, but....

(Nice deal since the seller thought the car was basically worth zero!)

gforce1108 said:

I've never seen a coil that was intermittent, but it is an aftermarket part (polar air, I believe?). It's a pretty simple electromagnet - coil is energized and it attracts the end plate, pulling it to make contact with the pulley. I expect some slippage as it first engages, but it seems like mine is slipping more when hot.

Hopefully someone else has had one partially engage.

Click to expand...

I replaced the coil on my Jetta (my other crazy project) last year and it has worked fine, since. I'm going to check all of the electrical connections, the coil resistance, but after spending a while last night reading over some threads, I'm wondering if the RCV is not functioning properly. I do not know how an intermediate shade-tree mechanic like myself can "capture" and "reload" the R134a which I believe is required when you change and/or pull and inspect the RCV. I haven't seen where someone captures the R134a and changes the RCV themselves while in their own garage. I need to figure out if I can go to a local A/C shop, have them suck out the R134a, I'll drive it home, inspect the RCV and replace it, if necessary, and then drive back to the shop to have them put the R134a back into the vehicle. If that is what NEEDS to be done, then I might just have them replace the RCV for me if they seem honest enough to actually look beyond trying to sell me a whole new system for $2K.

-Mike

To recharge these systems successfully you MUST be able to evacuate it entirely before charging (which means you need a good vacuum pump) and then you need a means to weigh the charge going back in, since you CAN'T properly charge these systems via pressures.

So yeah, if you intend to do things legally you need to find a shop that will evacuate the old refrigerant for you, since venting it intentionally is illegal, then change the RCV (AND dryer!) then either have the shop reload the refrigerant or, if you have the vacuum pump and a means to weigh the charge going in and a set of gauges you can do THAT part yourself.

csstevej said:

I also have had this happen, it started about 3 days ago. I had the burning rubber/ electrical smell with squealing when first started for about 20 seconds then be fine.
I had just ordered today a new clutch pulley for Wednesday delivery, went for pizza , picked up pizza and car would not turn over, sounded like a dead battery.
Needed to cut accessory belt off and car fired right up. Drove the car home the 7 miles with no power steering and battery light on.
Word of advice if it's making noise don't drive it, just my .02

Click to expand...

Last year when the bearing failed, that's what I ran into. Huge plume of smoke coming from the pulley. I actually poured water on it to cool it off. In this case - the pulley is spinning fine (it's always spinning regardless if the AC is on or not) - the 'sparks' are from the end plate trying to engage the pulley. I just can't tell if the compressor is locking up or if the clutch isn't engaging fully (incorrect shimming of endplate / weak coil).

Genesis said:

Yeah a friend of mine got a Golf that allegedly had a locked up engine.
Well, the ENGINE wasn't locked, but....
(Nice deal since the seller thought the car was basically worth zero!)

Click to expand...

I was very close to it completely failing last year - I had 2 BEWs in the 'shop' within a week for the same pulley bearing failure - one got hot enough to transfer heat to the belt and melted the tensioner pulley.
I would like to see some information on setting up the end plate gap. I would think if the compressor was locking up there would be a noticeable load placed on the motor - nothing was out of the ordinary other than the lack of AC and the whiff of a burning smell

I just got mine off today, my coil is melted and the bearing is bone dry and missing some balls. Once I figure out how to post pictures I'll post some carnage if it's ok with gforce.
I also would like to see some info on that shimming.
Just a note I had just changed this set up about 2-3 years ago.

The only thing I could do last night was to turn on my ignition key, (car not started) and turn the A/C button on with the fan speed set to 1. Only the smaller, passenger-side fan came on. I performed this test on my Golf (the car with the A/C issue) and my Super Jetta. Both only had the smaller A/C fan running. I'm wondering if I'm performing this test incorrectly... but I don't think so. I believe I might have to rebuild and/or buy a couple of the large fans. Darn...

Yep - when one fan runs both should run. There is no wiring setup that allows for only one to run, so if you have one running the other is broken.

Most of the time the large one fails; the problem is that this will NOT disable the AC system, but what it WILL do is overload it, and left unattended it will eventually destroy the AC compressor. Make sure those fans work!

Genesis said:

Yep - when one fan runs both should run. There is no wiring setup that allows for only one to run, so if you have one running the other is broken.

Most of the time the large one fails; the problem is that this will NOT disable the AC system, but what it WILL do is overload it, and left unattended it will eventually destroy the AC compressor. Make sure those fans work!

Click to expand...

Yep. I'm going to replace both of them if I can't get them to work by jumping them directly from the battery. Last year, I looked at replacing the FCM. I'm still trying to figure out what happened the other day which almost mirrors the OP's issue. Stay tuned!!!

I haven't gotten any deeper into this yet. I have my 03 ALH wagon in the garage for DMF replacement along with a complete suspension refresh. And I kinda bought another car with working AC

I'm still convinced it's related to the shims - perhaps I damaged the face plate by letting it slip too much.

When I did mine , one shim was too tight. I added another and it was fine.
The clutch kit I got had several shims with it, they were all the same thickness.

csstevej said:

When I did mine , one shim was too tight. I added another and it was fine.
The clutch kit I got had several shims with it, they were all the same thickness.

Click to expand...

Good to know... mine didn't come with any. The seller mentioned that they were going to add them to future kits. I believe I found the same issue - one was too tight so I went with two. Hopefully I'll get it back in the garage shortly to get it figured out.

I ordered a couple of the large driver-side fans from RMeuropean and installed the first one on the Golf last night. Now that both fans run, I can work on the compressor clutch/coil. I ordered both the face plate and the coil off of ebay yesterday and should get that Monday. The coil was open so once I replace that, hopefully the thing will work again. It doesn't make sense to me that the coil would just go bad (ka-blammo!) that fast, but maybe the heat was just too much for it. Perhaps by next Monday or Tuesday night, things will be working again. I'll replace the big fan on the Jetta tonight and be happy that both fans are replaced and at least the Jetta has working A/C for now.

Good luck with your fixes.

-Mike

I would recommend changing the pulley or at least the bearing in the pulley too. I replaced 2 coils on 2 higher mile TDIs over the last 2 years and both had bearing failures within a year (over 200k miles). The heat generated by the bearings killed both new coils.

I now will replace bearings with the coils.

Yeah I will up to doing three of these, I just order the kit and change everything .

gforce1108 said:

I would recommend changing the pulley or at least the bearing in the pulley too. I replaced 2 coils on 2 higher mile TDIs over the last 2 years and both had bearing failures within a year (over 200k miles). The heat generated by the bearings killed both new coils.

I now will replace bearings with the coils.

Click to expand...

Yeah. I ordered the kit with the bearing and the pulley. Didn't mention that. It just makes good sense to replace all of that when it's all apart on the floor.

Pulled the compressor down on the Golf this weekend, changed out the clutch face, pulley (w/ bearing), and the coil, tested the coil operation for smoke w/ a battery, all worked quite well. Put everything back together w/out issue. Took my time, didn't curse/swear at all. A/C blows cold. Oh, and replaced the large fan on both this Golf and my Jetta. RMeuropean had them for about$52/ea. Not too bad of a job replacing them.

I still haven't gotten to fixing my Jetta yet. Working on everyone else's cars and not my own... 03 Wagon looks like it exploded in the garage. One of these days...

Now when it's really hot I take the SLK