When I started driving home this evening, I noticed the dashboard illumination and headlamps both seemed a bit dimmer than usual but it wasn't until later, when I held the main and dipped beams on simultaneously for a few moments and the ABS/ESP lights came on, that I realised I had a problem. When I let go of the dip stalk, the warning lights went out but when I pulled it again, they came back on. I figured I had a voltage problem, so killed the main beams, air con and radio, and decided to get home as quickly as possible. The wipers eventually began to slow and judder a bit, but I managed to keep the warning lights off again until I pulled into my road.

When I stopped the engine, the interior light seemed to be its usual brightness and the doors locked with the usual clunk, as opposed to the sluggish one that usually accompanies a flat battery. In fact, the battery is only a couple of weeks old, leading me to think that the problem I have is that it is not being charged. Oddly, though, the battery light on the dash is NOT illuminated.

On the way to work this morning, I was caught out by a puddle that was rather a lot deeper than I expected. Such "splash" moments usually cause the auxiliary belt to slip for a few seconds (is this normal or have I lost a cover somewhere?) but I heard the reassuring squeal telling me that it had started spinning again. This wouldn't have done any deeper damage, would it?

I need to use the car again tomorrow morning. What should I check? I'm on my way to look at the black wire on the exterior fuse box, and the 110A fuse, now. Anything else? Has anybody else experienced a failed alternator or is it more likely to be the wiring loom?

Thanks in advance.

Put a multimeter on the battery with the engine running. It should be 14v ish then turn everything on (lights, radio, AC etc.) and it should drop no more than 13.5v ish

The belt squealing isn't normal unless you're driving through giant floods, replace the belt and check the tensioner.

I've got an alternator if your anywhere near York

Thanks, Frisco.

The problem is the crimp on the end of the black lead from the alternator to the exterior fuse box. The cable has sintered and stopped conducting. That can be easily fixed by stripping back to good copper and re-crimping (or perhaps even soldering).

However, in the process, it has also got hot and melted part of the fuse box housing in such a way as to make removing the 110A fuse impossible without destroying it. The fuse box is actually quite salvageable (it was just melted edges "hanging on" to the fuse, which have now been removed) but the fuse needs replacing. Is the fuse a dealer-only part?

It's common apparently, mine was melted too. £10 on ebay for the entire box mate

Wow, that's cheap although I couldn't find any for less than £25 and there seem to be a lot of variants. I'll probably just replace the fuse and leave the box in place.

Any idea how much the fuse will be and whether it's a VAG-only part?

hmm odd i have the same problem, but i done the multi meter thing, when i started the car i battery was reading 11.88v then when i reved the car up it went to 14.~ v then i put the lights radio heating on and it went too 13.75, but if i dont rev the car the lights are very dim... if i leave the car running for say 10~15 minutes the abs light comes on and my radio starts cutting out, but if i disconnect the battery the car still runs, this is odd, also my battery warning light flashes on and off when i use the light and heaters when driving, but when idling the battery wont charge

I'd first try cleaning up the terminals on the alternator and the earths from the battery to the chassis

hmm odd i have the same problem, but i done the multi meter thing, when i started the car i battery was reading 11.88v then when i reved the car up it went to 14.~ v then i put the lights radio heating on and it went too 13.75, but if i dont rev the car the lights are very dim... if i leave the car running for say 10~15 minutes the abs light comes on and my radio starts cutting out, but if i disconnect the battery the car still runs, this is odd, also my battery warning light flashes on and off when i use the light and heaters when driving, but when idling the battery wont charge

I would check all the connections, crimps and cabling. Sounds like something has got a higher resistance than it should have...

I have ended up buying a new cable after stripping and stripping back insulation and finding very little in the way of good copper. It was £38 from TPS; part number 1J0971349GN, which is the one with the extra 4 wires (2 for the alternator sense pins and 2 for the air conditioning compressor).

I'm about to go and fit it now. Any idea what route the cable follows?

Well this is turning into a real pig of a job. After nearly an hour, I've found and prised apart all the connectors with their finger-killing clips, removing the battery box in the process. The one thing that I'm stuck on now is the final clip that holds the cable to the alternator - not the electrical connection, but something else that bends the cable into a U-shape. I can't see it and I can't feel a way in. Any pointers?

It might be the thing near the bottom-centre of this picture. Still can't see how to undo it, though.

That thing at the bottom of the picture would just be held on with a bolt/nut I would have though. I removed my alternator a year or two back, but I can't remember there being anything too complicated about it though, so that doesn't really help.

Have you got a small mirror you could use to help improve your view?

Thanks for the suggestion. (Off topic, I've spent most of the last few years thinking you were "M. Barnes". I must read more carefully!) EDIT: It felt like there was a nut behind it but I couldn't get a socket or spanner in there without removing the alternator.

I gave up in the end, left the old cable in place and just tied it back out of the way. Neither end of it is connected to anything so it isn't doing any harm, it's just rather dissatisfying. It's been raining all day, though, I'm cold and wet, and was due to leave to visit my parents hours ago, so this will have to do for now!

Edited 22 December, 201213 yr by will_

Thanks for the suggestion. (Off topic, I've spent most of the last few years thinking you were "M. Barnes". I must read more carefully!) EDIT: It felt like there was a nut behind it but I couldn't get a socket or spanner in there without removing the alternator.

Actually the B is my middle name :-)

Maybe a bit late now, but here is a picture of my slightly larger alternator (from my diesel). From that it would suggest you should have been looking for a nut to remove.

A belated thanks for the picture.

The saga continues. It worked fine for a couple of weeks but this afternoon the alternator light came on while I was on the motorway. I've made it home without any other warning lights so battery voltage isn't yet so low that other systems are shutting down.

Have I just been really unlucky? A new battery, a new charge cable (alternator to battery) and now, seemingly, a new alternator, all in the space of a month.

EDIT: I found a useful list posted by mbames in another post.

Battery light = knackered battery, duff alternator, high resistance in alternator wiring, issues with the aux belt/tensioner, freewheel pulley

The belt isn't squealing and the alternator is definitely spinning. I guess that leaves brushes, regulator or altogether-knackered.

Questions:

1. The Haynes manual says I "might" need to remove the power steering pump. Do I? 1.8T 4x4 (ARX) with air con.

2. Before I remove the alternator, does anybody know what power I'm likely to have installed? GSF sell 70A, 90A and 120A units.

Edited 5 January, 201313 yr by will_

Have you had battery tray out and cleaned earth cable up yet where it bolts to body and engine

On my way out to the car now to measure voltages to begin with.

When the alternator spins, should the coils of wire that are visible through the ventilation holes move or are they static?

IIRC when I took the alternator out I had to remove the power steering pump on my TDi in order to get a one of the bolts holding the alternator on. In order to get the pump off you need to get at the bolts which hold the pump on which are behind the pulley which drives the pump, so BEFORE YOU REMOVE the aux belt you have to loosen the bolts on the power steering pulley. Then take the belt off, remove the pulley from the pump and undo the pump mounting bolts.

I think that I loosened off the alternator and then I could get at the lower nut which holds the cables to the alternator, the I took the alternator out of the car. I think I also removed the fans from the radiator to make a bit more room.

If the petrol engine is like the diesel the alternator has to out of the top of the engine, the bracket which holds both the alternator and aircon compressor stops you taking it out the bottom.

As for the output of the alternator, it should say on it, on a sticker on the side. Failing that ring a dealer / TPS with the part number (which is on the end and visible in your photo) and ask them

On my way out to the car now to measure voltages to begin with.

When the alternator spins, should the coils of wire that are visible through the ventilation holes move or are they static?

I think they should move, there should also be a fan thingy visible (towards the pulley end which should obviously rotate).

Thanks, Volvomeg and trundlenut.

It turns out that on the 1.8T petrol, both the power steering pump and the air con compressor are underneath the alternator, so all I had to remove to get to it was the throttle body (which is easy - two jubilee clips, on electrical connector and four 5mm allen keys, all with easy access) - and the auxiliary belt, of course. Note to others: I could only get the tensioner out the way once I'd removed the throttle body and hacksawed a 5mm drill bit slightly shorter so that I could get it past the washer bottle into the hole.

I've removed the two large (13mm) bolts holding the alternator on (note to others - you'll need to use a spanner on the top one as there isn't space for a socket) but the damned thing will not budge. It feels like it's still bolted on (firmly!) but I think it's just seized to the bracket. Any tips, other than just "hit it with a hammer!"?

In mine, the coils don't move but I can see the fan blade inside them moving. It doesn't feel like anything's obviously broken.

I've taken the opportunity to clean the throttle body but still can't get the alternator off!

Here are some pictures showing how removing the throttle body improves access, and how to use a (shortened) 5mm drill bit to hold the tensioner out of the way.

Now, why won't my alternator budge?

Put a pry bar / big screwdriver / crow bar between the alternator and the mounting bracket and carefully encourage it out.

There are sort of floating bushes (don't know what the technical term is) which are pulled out against the mounting bracket when it is tightened up, when you remove the bolts the bushes don't move and thus keep it held in place.

I used a big G clamp to push them back in before I re-fitted the alternator.