# How To fix an Aircon magnetic clutch



## John-H (Jul 13, 2005)

*How To - Repair an Air Conditioning Magnetic Clutch *

This might help someone. Recently a horrible noise came from the engine bay of my TT like a worn bearing vibrating - a bit like a worn out toy car wheel that wobbles on its axle when spun rather than just rotating. This was my magnetic clutch wearing out on my air conditioning compressor - shook the whole car when it happened. Turning the aircon off stops it if you are lucky but it can start vibrating again. Eventually it did it again followed by a clunk as it fell off.










What happens is that when the clutch wears out it gets hot and overheats, melting the nylon in the nylock nut, which then becomes loose. The early design seems not to be splined on the shaft, so the whole thing spins and wears loose - hense the horrible noise as it vibrates and wears the shaft barrel shaped. Eventually the nut falls off followed by the clutch plate.










Luckily on the TT it's retained by the engine under tray cover.

Here's a new kit I got for my S3 for about £65 from eBay which includes the pulley and magnetic coil.









P/N: 1J0 820 811 M

You can see the clutch plate with the later revised splines. There's a small fitting kit with nut, circlips and shim washers. P/N: 1J0 298 012

The early TT APX does not have a kit for magnetic clutch replacement it seems - possibly because of the damage caused when it fails and there is a revised compressor which then does have a replacement clutch kit.

1J0 820 803 A - Compressor SANDEN (replaced by 1J0 820 805 - compressor + 1J0 820 811 A - mag clutch)
1J0 820 811 A - magnetic clutch >>8N-Y-030 000*
1J0 820 811 L - Magnetic clutch F 8N-Y-030 001>>*

Both my TT and S3 were SANDEN compressors.

That didn't help me. A new compressor is a big job because of all the gas refilling and disassembly and the compressor is very expensive unless you get a second hand or reconditioned one.

Note: This first method with epoxy was bettered by second key shaft locking method - see later

What I did was a bit of a bodge but if it works and extends the life of the original that's fine. First, the friction plate was a bit bent because of all the vibrating - the triangular part riveted to the boss and holding the spring fingers. The outer friction ring was pushed away from the correct position and nowhere near the pulley face. I bashed it back straight with a hammer against an open vice so it then sat flush on the pulley and required the right shim washer to give about <0.5 mm clearance (spec 0.2 - 0.8 mm). The steel ring was still thick enough to be attracted by the magnet and the clearance is more set by the springs than the thickness of the metal. The nut and shaft needed the threads cleaning up with an M8 tap and Die, counter holding the shaft with small pair of Mole grips.

The clutch boss was a sloppy fit on the barrel shaped shaft. Giving it a clean and a roughening, I coated the shaft and inside the boss with Plastic Padding Chemical Metal to take up the play and lock the clutch to the shaft. Rotate it on to evenly spread the epoxy and centre it making sure you don't get any on the threads. Clean off quickly with IPA soaked kitchen towel if you do. I held it nipped into place with the old nut whilst it set.

Then I took the nut off and added some thread lock to the old nut and clamping the clutch plate to the pulley to stop it spinning, managed to get the nut very tight - enough to clamp the boss to the shaft without the need for the Plastic Padding. The plastic Padding is only really necessary to stop the shaft spinning as you tighten it. You need to lock it somehow otherwise it may not become tight and the chances are you can't then get it off again to have another go because the shaft spins!

Anyway - it works fine again now. I hope that helps someone - it's actually a very cheap fix 

EDIT: when doing my S3 I found that the shaft was also not splined - despite the kit being "the right one" for the compressor. Not daunted, I widened the splined hole in the clutch plate. This is easily done with an M12 tap and taking the burs off with a file. It's then a good fit and a good key for the epoxy and using the exact same method. The S3 works now too 

Note: Use this key shaft locking method - far better:

EDIT 2: The TT is fine and the S3 worked well for couple of weeks following a re-gas to get it up to spec but unfortunately the clutch came loose again. I'm guessing that the epoxy may have been holding up the boss under the pressure from the nut but eventually degraded and came loose. It should have been metal to metal contact at both ends of the boss so shouldn't have moved.

I took the clutch off again (tricky because of the spinning shaft) and this time cut a 5 mm diameter half groove in the pulley boss as shown and made a half round tapered pin key. I ground a flat on the shaft (which was the easiest thing to do in the tight space) using a Dremel with a parallel sided diamond grinder of about 5 mm diameter.


























A bit of adjustment of the tapered key with some emery cloth and it could be tapped in for a snug fit and clamped up tight with the nut and with no chance of the shaft turning. I don't think this will come loose


----------



## maltloaf (May 8, 2015)

Hi John,

as per my thread in my signature, I'm diagnosing my air con at the moment.

I think my clutch may have fallen off as all I can see is the threaded end and it looks very much like your picture.

I'm a bit confused which kit I should buy to replace the missing items. I'm confident everything else is right now, the fans kick in and the system is gassed, but obviously the compressor can't engage.

Many thanks,

malty


----------



## loremipsum (Nov 6, 2015)

You rock! Thank you!


----------



## John-H (Jul 13, 2005)

maltloaf said:


> Hi John,
> 
> as per my thread in my signature, I'm diagnosing my air con at the moment.
> 
> ...


Hi Malty,

That was the problem I had. There was no Kit available for my TT and the shaft had no splines. My S3 had a kit available but the compressor shaft was exactly the same as my TT - also with no splines but the kit did have splines - so needed adapting to fit.

Since writing the guide the clutch plate on my TT came lose again. It had lasted for quite a long time but perhaps the original was wearing thin and slipping so got hot again and destroyed the stud lock and fell off.

So I bought the same kit I got for my S3. The part number is:

1J0 820 811 M

£54.99 from eBay. It includes the magnetic coil but you only need the clutch part really:

http://m.ebay.co.uk/itm/201528864723

I performed the same modification with the half round key which makes for a solid shaft locking method and has the advantage that you can take it off again afterwards if needs be. I'd do that if I were you - don't bother trying epoxy as there's too much risk of it not locking the shaft or coming loose in service.

Don't forget the fitting kit which you can get from Audi and doesn't cost much - part number:

1J0 298 012

That includes a new locknut and selection of shim washers. I didn't use the circlips as I didn't replace the magnetic coil.

I hope that helps you.

Regards,
John


----------



## marks72 (Dec 22, 2016)

Hi John, I'm having exactly the same issue. Currently the car is stranded with a terrible noise from the AC unit and the nut half on and half off. I was wondering how you lock the centre shaft as it just spins when you turn the nut.
Any help would be great.
Cheers
Mark


----------



## Farseer (Dec 3, 2018)

Hi, John!

Goodness me, your guide(s) always comes as a relief when I find a problem in my TT and I desperately search the Internet for clues.

I, too, have "lost" an a/c clutch, although when that happened is a good question indeed.

I will get to repairing the a/c (and if not I, then the mechanics, but, thankfully, I won't be scammed as I know full well what's missing and how to replace it), but I have a very important question; what thread pitch is the M8 die?

My stud doesn't need cleaning up; the beginning of the stud has disappeared under a blanket of corrosion, and only after 4-5mm do I see preserved threads. I can only find 1,25mm pitch M8 dies in my local shops, so I am wondering if this is a standard, or perhaps the studs in the a/c are 1,0mm, and not 1,25mm, although, it's hard to discern a quarter of a milimetre.

If you could remember what thread pitch your die was then it would be God-sent.

All the best.


----------



## John-H (Jul 13, 2005)

M8 x 1.25 standard metric not fine.

Make sure that you can still rotate the shaft round easily. The clutch fails either because it's worn out and eventually starts slipping and overheating - or there is compressor failure and seizure which rapidly overheats the clutch. Either way it overheats and drops off.


----------



## Farseer (Dec 3, 2018)

Thanks, John. I went out and got the die. I'll get to it this evening and hopefully come back with good news.

As for the shaft... I can't twist it with my fingers, that's for sure, and it's hard to get a set of pliers there. If it's seized then I don't think I'll bother with repairing the damn thing.

Last question, you did this from underneath the car, correct? I managed to find enough play to work on the a/c by taking out the charcoal filter (?) (the black box next to the power steering fluid reservoir). I'm wondering if taking the wheel off and that plastic "sheet" would be a better area of approach.


----------



## John-H (Jul 13, 2005)

Yes, I worked from underneath, I think with the front wheels on ramps, the under tray and plastic side guard removed then you can get to the pulley. I even managed to machine a flat on the shaft with a mini grinder. Hopefully you have the later one with a splined shaft.


----------



## A_Banging_Donk (Apr 22, 2017)

I did this recently, splined and keyed clutch hubs available on eBay, 2000 APX with splined hub here.

A word of warning - fresh regas and a new clutch with broken low speed fans is a recipe for disaster, condenser got very hot in traffic, spewed out a ton of refrigerant from a relief valve on the compressor head.. make sure your low speed fans work!


----------



## Farseer (Dec 3, 2018)

Thanks guys for your help. My a/c comes splined but they aren't really that visible due to the effects of corrosion. I cleaned them out as best as I could using elbow grease, a stiff wire brush, and some de-rust chemicals, and we'll just have to see how it all goes.

Fans thankfully work on low!


----------



## Farseer (Dec 3, 2018)

Hi, guys.

Regrettably, sad news.

I honestly dislike going to the mechanics for whatever reason, as I told them explicitly when leaving the car that the splines were gone, to which the assured me that it wouldn't be a problem. They then call me in the morning telling me exactly what I told them and that nothing can be done about it...

Anyway, they charged a ridiculous amount for a rebuilt compressor. I'm in Poland currently, so a new compressor costs around 700PLN (150 quid) and they were asking for 1100-1500 for a rebuilt one whilst charging around 2000-3000(!) for a brand new one... ridiculous.

So I just asked them to de-gas the whole system (which he agreed reluctantly, probably realising I'll want to do it myself). I'll buy a used compressor (one with splines and working!), swap the clutch out for the new one I have, hook everything back up, and then go to another shop to have the system filled.

Thank you all for your help regardless.

Have a good one!


----------



## John-H (Jul 13, 2005)

You could keep the new clutch as a spare. If the replacement is working why change it? They are tricky to set up and are esy to either have slip when engaged or have partial engagement when off, both of which can overheat.


----------



## Farseer (Dec 3, 2018)

I was just thinking that since it will be on the table I could easily just replace the clutch not knowing how much life in it is left, but you have a point.

I'll look around the Internet and see what else I could change whilst there (o-rings etc.), exploiting the fact that the system is de-pressurized.

Sorry for sort-of hijacking this thread, but some aspects were told more in-depth now, and if anyone ever has doubts in regards to splines on the shaft they'll see my posts and be all the wiser than I was. :mrgreen: Cheers!


----------



## John-H (Jul 13, 2005)

The clutch is very slow to wear. It's a case of setting the correct clearance with shims under the pulley boss. You can get a set of different thickness shims from Audi.

They usually recommend replacing the dryer with a new compressor to remove any moisture to stop corrosion. There are different sizes of o-rings for both.


----------



## Taylortony (Feb 10, 2012)

If anyone needs one I have a mk1 air on pump Assy, new and complete unopened in the box, it cost me £99 off eBay, is a ford version and comes from a Uk main dealer franchise, never fitted as I part ex 'd my mk1 for a 2 shortly after.


----------



## John-H (Jul 13, 2005)

One for the market place  There were two makes for the Mk1 I seem to remember.


----------

