Hi,

I've just had my aircon compressor changed by a local garage (not VAG specialist) who I have not used before; I have little choice in my current location. I provided all the notes but had to trust them to do the work due to the refrigerant issues. I now have aircon once again although not as cold as I seem to remember it. The biggest problem is that the auxiliary belt is now vibrating and the damper nodding up a down as result. The vibration is less with ECON selected, but still quite alarming.

The belt apears to be aligned, and the alternator freewheel feels as if it is working. This leaves an oscillating compressor or a suddenly ineffective damper.

The car is going back to the garage but I would welcome any views or previous experience so that I can speed the diagnostics.

What was the problem with the compressor? If it was the pulley, it could have knackered the tensioner. Alternatively the alternator pulley could be on its way out, just because it hasn't siezed doesn't mean it is OK, on my car the pulley seemed OK but when I removed the alternator and fitted the new pulley you could tell the old one was on its way out.

I don't think they could have fitted the compressor wrong.

I changed the alternator pulley on a 130PD and the tensioner seemed OK, but within a few days it had started vibrating so I had to change it, then all was good.

I think its probally the belt tensioner.

A very crude way of testing the tension of the belt is to see if it turn to 90 degrees with relative ease (obviously engine stopped!) if it goes over this, once again without massive force used then its slack and true enough most likely one of the older pulleys will be on its way out.

The alternator can make a slight drone noise when the bearing is starting to go but over a diesel this could be quite hard to hear, if like many of us you have not got the specialist equipment (stethoscope) then a long screw driver will do the job or telling you if the bearing is starting to go, place it on the metal of the housing away from any moving parts and put your ear on the other end.

Thanks to you all. I think you are correct about the tensioner. The vibration is worst on tick over, and really bad with the aircon on. As the revs build the belt rapidly returns to normal behavior. I have ordered a new tensioner and belt, as they are both 7 years old. I'll fit them next week and I'm fairly confident it should work. The compressor was expensive enough, this just adds to the pain.

Thanks again for you help and advice.

Mike,

Thank you for the info. I have just taken the old tensioner off the car and it is not the same as the one I have picked up this afternoon from the aftermarket place. With the belt off I could not get the alternator pulley to show any signs of a freewheel capability and now have doubts that the tensioner is causing the problem (seemed to have plenty of resistance). I presume the freewheel should work simply by spinning the alternator by hand. I also understand that a special socket is required to remove the unit. Not sure if anyone is able to confirm for me?

Mark

Assuming the alternator is the same as on the mkI, you should be able to spin the alternator then grab the pulley and the alternator will continue to turn. So it sounds like the pulley on yours has had it. Though it should only freewheel on way.

You do need a special tool, something like the Sealey SX401 kit (though there is a cheaper version IIRC) to get the pulley off. The middle part of the tool holds the shaft on the alternator then a splined socket slides over this to engage with the splines on the pulley.

On mkI you have to remove the alternator to get the tool onto the pulley. If you can do it in the car on the mkII that should save you some time but you may need a lot of brute force to release the pulley.

Finally, got the required parts and have changed the alternator pulley. All sorted! I bought a Laser 3404 tool that cost £13.50 on Amazon and it worked brilliantly. I had to use a breaker bar to free the pulley after the 6 years that it had been on there. The Laser tool comes in 2 varieties; one with a T50 Torx shaft and the other with an M50 spline shaft. I think the 1/2" spline external socket is the same on both. I almost ordered the wrong one until I took off the pulley cap and tried some screwdrivers in the end of the alternator shaft - does not seem to follow the advice on the websites so try it out first.

Many thanks for all the help - it prevented me spending on the wrong item. Sadly the aircon has stopped working again, so back to the garage for them to find the leak!

Hi everyone, sorry to bring an old thread back from the grave! I just stumbled across this and it describes a problem I'm having perfectly.

 

A rattle which is much worse at idle revs, and which I've managed to pin down to what looks like the tensioner on the aux belt. The tensioner and the belt when near it, are both juddering around like mad, which is making the alternator rattle a fair bit too, but it seems to be worst at the tensioner.

 

After reading this thread I went to see if switching the air-con on and off made any difference, and it does indeed make a big difference. When I switch econ off the rattle goes crazy. It seems pretty conclusive what the problem is, so this is just an idle question really. Can anyone explain to me why the air-con makes such a big difference to the problem???

 

I have a pretty basic understanding of how engines work etc, but I can't make the connection between the air-con being switched on and needing more power, and the rattling tensioner! I'm sure I've missed something....

 

Cheers.

There isn't a clutch on the compressor so it spins the whole time. I would still suspect the alternator pulley is the cause.

I assume the aircon works?

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Just for information, one way clutched alternators were/are fitted to diesel engines that have a dual mass flywheel. A side effect of the DMF is that at idle and no load, crankshaft rotational speed is not constant over a complete revolution of the crank, but speeds up and slows down. This is because the real flywheel (before the dmf) at the crankshaft end is very low mass.

Cheers guys sorry for the slow reply. Yep the aircon does work as far as I know, although I've only just got the car so obviously haven't had to test it much at full-on low temperature etc. I have checked briefly though and it seemed to be ok.

 

I found this video which seems to show exactly the same problem that I'm having.

 

 

If you watch it, roughly around 11-13 seconds in, the camera stops moving and you can see the belt flapping about on the left of the screen as it goes round the tensioner. So I assumed the tensioner was the problem. But it's possible this vibration is passed on to the tensioner from a dodgy alternator pulley?

 

Unfortunately mine's a mk1 (I know I'm in the wrong place haha) and I think earlier in the thread Trundlenut mentioned that on the mk1's the alternator has to come out to get the pulley off. It's actually booked in for a cambelt change tomorrow though so I'll get them to have a look while they're there.

When the pulley went on my old mkI, having the air con on made it worse.

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Yep I think you guys were right. Just on the off-chance I sprayed a bit of WD40 on the alternator pulley and it did make quite an improvement so that's pretty conclusive. Obviously only a temporary fix though so the garage are hopefully going to sort it while they're doing the cambelt change today. Thanks for the info everybody.

People on Ebay are advertising the Torx T50  clutch pulley tool as suitable for a whole range of VW stable cars. It is NOT suitable for my alternator on a 2006 Octavia2, which has a 12-point 10mm spline socket in the alternator shaft. I sent a question but the seller did not respond. I suspect that there are NO VW stable/Bosch alternators which use the Torx T50.  Anyone know any different? This tool is 8.8mm diameter; it would mesh very sloppily in the 12-point spline but could very easily damage either tool or shaft,

Edited 16 June, 201510 yr by spiney2

Just wanted to add to this thread that I came here when my belt was still squeezing even after changing the tensioner.

 

I bought a used alternator , took under an hour all in to swap (1z 1.9) and squeel has gone.

 

Everyone I asked was convinced it'd be the crank pulley.

 

Now going to refurb the old alternator as a spare.

 

Cheers all