Air conditioning failure - clutchless/variable displacement compressor failsafe in pulley?

[the sheep]

The AC has stopped blowing cold on a 2003 Audi A6 C5 1.9tdi AWX. After a lot of internet searching and car poking I think I've found the problem. Any help confirming it would be excellent!

It's a Denso clutchless compressor, is the bolt in the centre of the compressor pulley supposed to rotate with the pulley?

Based on some of the info at the following link it appears that for clutchless/variable displacement compressors the pulley has a failsafe so that when a torque value is exceeded (eg the compressor is jammed) it breaks some rubber component so that the pulley can continue to rotate and not cause further damage. I'm guessing that the bolt in the centre would be directly attached to the compressor shaft and it not moving with the pulley indicates that the compressor is no longer being turned, hence no cold air. If anyone can confirm that before I buy another compressor it'd be great!

http://www.alanko.de/dateien/Clutchless_Compressors.pdf

Video showing pulley and bolt with engine running:
denso ac compressor pulley - YouTube (http://youtu.be/VAF8-Arpm2M)

Image showing pulley stationary:
http://i1383.photobucket.com/albums/ah290/sheepapparently/IMG_1628_zpspk0avqfp.jpg (http://s1383.photobucket.com/user/sheepapparently/media/IMG_1628_zpspk0avqfp.jpg.html)

Background info:

The only VCDS faults in the HVAC section were for a faulty air quality sensor - I didn't see how this would stop the AC
I've had the car for a year, I'm not sure if the AC was ever serviced before (now 12 years old).
Late last year the cap on the front of the compressor pulley fell off, I found it and the securing bolt on the engine cover and refitted and the AC worked again fine, it then fell off for a second time so I put some thread lock on it and did it up tight. It's been fine until last week!
The electric auxiliary fan does not run, there is power to the connector but the fan doesn't run - I think the fan is toast but doesn't look to difficult to replace (eurocarparts have EIS ones for ~£50). I don't think this is the reason for the AC not running - I would have thought that the AC would turn on for a bit before cutting out, I've tried running the AC on the motorway where there should have been plenty of cooling flow and it still didn't work.
I had the system regassed initially, it didn't work but I forgot to ask whether there was already pressure in the system before they tried to put new stuff in.
The econ light goes on and off fine - doesn't seem to indicate a failure with the low pressure switch or the system being low on gas

[mrnice]

I'll be reading this with interest as I have exact same spec car with exact same symptoms even the same error code. My plan was to replace fan and either compressor pulley or whole compressor (not sure pulley is available seperately). For what it's worth my system still has pressure (although how much I haven't checked. Been on my to do list for a few years....

[the sheep]

Good to hear that I'm not alone with the problem!

I have found this on a BMW forum, interesting to see a pulley cutaway and from what I can tell from the external faces it looks similar to the one fitted to our cars. Although, if it is the same, the only explanation for the spinning in the video seems to be that I've separated the splined section of the outer plate from the rest of it, probably because I did it up so tight previously to stop it falling off again...

Any more theories?

Anyone here changed an AC compressor on a 545i? - Bimmerfest - BMW Forums (http://www.bimmerfest.com/forums/showthread.php?t=677877)



http://i1383.photobucket.com/albums/ah290/sheepapparently/Screen%20Shot%202015-04-15%20at%2015.27.27_zpsshogy36i.png (http://s1383.photobucket.com/user/sheepapparently/media/Screen%20Shot%202015-04-15%20at%2015.27.27_zpsshogy36i.png.html)

[mrnice]

I'd assumed that on mine the rubber element fail-safe bit had broken, maybe due to compressor seizing, planning to take compressor off to investigate further (again when I get around to it!).., good to know fan is £50 from euro, cheers for tip

[ceilidhalfie]

Hi guys. Cannot help with the AC compressor - the one on my Allroad is the clutch type. The ELECTRIC FAN runs all the time - at start up at low level and then boost if coolant temp mandates this. The electric fan not working does not affect the AC - it is really needed when IN HOT CONDITIONS the engine is idling for any length of time or when you are slow moving and the viscous fan cannot keep coolant cool. I ran with mine not working for years before I realised the above when sitting in a hot car park in southern France with engine and AC running. Coolant started to overheat! The constant running eventually gooses the carbon brushes of the fan. It is easy to replace - one screw at 11 or 1 o'clock (cannot remember) on the fan and an anti-clockwise turn to release and remove. Can remove with everything in situ but best to put front in service position if you are picky like me and you want the wiring positioned as before.
Given the above, as this fan will use some (little) fuel, I disconnect it in the winter. Have you guessed yet that I am from north of the border!

[the sheep]

Sounds like I need to get the fan replaced ASAP before it gets warmer. Cheers for the input ceilidhalfie.

I have a new theory. If the plastic/rubber breakaway component were to have failed I would expect to see the whole front plate not spin with the engine rather than just the compressor axle. In the video linked in the first post you can see the front plate moving with the pulley while the bolt remains stationary.

The only explanation that I have for this is that I've separated the splined section of the front plate that connects to the compressor shaft from the rest of the front plate. The front plate seems to be made of two parts in this replacement part http://www.mavoyparts.com/CLUTCH_COVER_6SEU12C_7SEU16C_Audi_VW_Skoda_Seat_Me rcedes_H19mm/p823544_8241742.aspx.


In a diagram shown on another forum (Automotive AC Information Forum - ACKITS.COM (http://www.autoacforum.com/messageview.cfm?catid=2&threadid=20076)) there are two washers that seem to sit between the front plate and the compressor axle. When the front plate fell of in the past I replaced it and the bolt which I found in on the engine cover but I was not aware of any washers. I'm thinking that if I missed the two washers and did it up tight (which I did to try to avoid it coming off again) I may have stressed it more than intended and broke the plate rather than the plastic component.


Am I making any sense?
Have you guys seen the two washers?


If the above is correct and the compressor isn't seized I may be able to just replace the front plate... which would be excellent

[Vik_93]

Could the infamous low speed judder on 2.0tdi models also be caused by this?

[mrnice]

That's one difference between our issues, the front plate on mine doesn't spin with engine at all, it's just loose (tho I can spin it by hand) having looked at the diagram you posted I guess your theory must be right.
As ceilidhalfie said, I'd want the front end off to remove fan, it would help with getting at compressor belt tensioner too but compressor easy to remove without moving lock carrier, I did it when replacing turbo to ease access.

[the sheep]

Seems to be solved - here's the update for anyone else with similar symptoms.

Fan
I replaced the auxiliary fan with an EIS one from eurocarparts - it doesn't seem as decent quality as the oem one that came out of it but it's easy to keep an eye on. The new fan now runs whenever the econ light is not lit. You can tell it's running when outside the car by the noise and I don't remember hearing the old one run for a while. Fitting it was a bit awkward but I didn't bother moving the front lock carrier into the service position. Would have been easier if I had but it was quicker this way. I removed the front section of the air intake, the top section of the timing belt cover and the bottom engine cover (just to route the power cable).

Compressor pulley
The front plate on the compressor pulley had not sheared. It turned out that the splines had been stripped. I think that they partially stripped the last two times that the plate worked it's way loose and there wasn't enough left to hold up.

http://i1383.photobucket.com/albums/ah290/sheepapparently/IMG_1662_zpsnycyqpzo.jpg (http://s1383.photobucket.com/user/sheepapparently/media/IMG_1662_zpsnycyqpzo.jpg.html)

The mating splines on the compressor shaft appeared to be fine (must be a lot harder) so for now I've just replaced the front plate with this one http://www.autoactools.co.uk/online-shop/featured-products/high-metal-hub-for-6seu12c-7seu16c and it's all running cold again. Removing the old plate was difficult because turning the bolt on the outside just span the compressor shaft (the plate didn't turn with it so you can't hold it still). I connected a socket up to a drill ran in reverse to get it off. I had to lower the compressor to get access to the pulley bolt with the drill.

I'm hoping that the combination of not having the aux fan working and the ac gas not having been changed or topped up as far as I can remember combined with the front plate spline being weaken by falling off the axle a couple of times was the reason for the spline failing. Now that it's been regassed (my first step in trying to get it fixed) and has a working auxiliary fan I hope it'll last a bit longer.

If the spline on the compressor shaft has been damaged I imagine that this plate will fail in the same way and I'll fit another £14 front plate and maybe put some JB weld or devcon on the spline. Alternatively it might turn out to be the compressor that was on it's way out the whole time...

Hope that helps someone else out there! I guess the moral of the story is check that your aux fan works and if the front plate from the compressor pulley does fall off, have a good look at the splines before just putting it back on.

Vik93 - not sure about the judder, I never noticed a judder problem with mine however I think some of the more modern engines have a different torque break away arrangement in the pulley. It has lots of small rubber pieces that can breakdown a bit before failing. The judder here was caused by play due to the rubber no longer taking up the slack. I haven't had the problem so don't know details but I came across the problem on forums when trying to figure mine out.

[the sheep]

mrnice- if you don't mind installing non OEM I found the following vendors selling parts that might get your pulley working again (assuming that the rubber section has failed):

Whole pulley:
http://www.autoactools.co.uk/online-shop/featured-products/direct-drive-compressor-pulley-and-bearing-6seu12c7seu16c-pb-166-vag
or
COMPRESSOR Pulley Clutch Audi for A4 A6 A8 (1.9 Tdi) - New | eBay (http://www.ebay.co.uk/itm/COMPRESSOR-Pulley-Clutch-Audi-for-A4-A6-A8-1-9-Tdi-New-/251791496770?pt=LH_DefaultDomain_3&hash=item3a9ff15642)

Rubber section (would require being riveted or bolted in place):
http://www.mavoyparts.com/CLUTCH_PLATE_6SEU14C_,12,16,17C___OD_83,9mm,_H19,2 mm/p823544_3850964.aspx

I guess there is a chance that it's just the rivets that have failed between the rubber section and the pulley. If so you maybe able to rivet or bolt it back without needing new parts. You could check the rivets by looking through the cutouts in the outer edge of the front pulley plate.

Good luck!