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Alternator hairy journey - twice!

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4.9K views 33 replies 12 participants last post by  Futura  
#1 · (Edited by Moderator)
Coming home from work last night and suddenly with a few miles to go my battery charge light came on :eek:

I selected 20C on the aircon and sure enough the battery voltage had fallen to under 12V, so I switched everything unnecessary off and got home Ok.

After a few tests I rang Audi and ordered a new voltage regulator 'next day' before connecting up my Accumate float charger to leave on overnight.

Driving into work was unfortunately dark but LED sidelights are bright and efficient and I kept the fan and radio off yet despite the precautions, on the motorway I suddenly got a battery voltage warning symbol. 20C showed under 11V and various other lights popped up coincident with indicating to change lane. Then my speedo and tacho started dropping to zero and I thought the engine was going to die but I kept going with little opportunity to stop safely.

Off the motorway now and frustratingly stuck in slow traffic but it was still going. A few jerks at the traffic lights and at the last section I turned my lights off to save it and pulled into the back of our building put it into reverse and the reverse light killed it - so I had to push to park next to the back door.

I'd brought an extension lead and my charger but checking the specs showed it was only 1.2 Amps peak which is fine for float conditioning but wasn't going to top up a 60 AH battery enough from flat in a working day, so I wired in a lab supply set to 14V to give me an additional seven amps in current limit. 8A x 6H = 48 AH so that should do I thought.

I went to Audi by foot at lunchtime and picked up the regulator.

Coming home was equally fraught however. Frustratingly slow traffic despite not needing lights still had me dropping volts alarmingly. Thankfully I made it and pulled into my garage with the engine starting to misfire and stutter so again I only just made it.

Changing the volage regulator was tricky. The bottom screw on the alternator cover I found could only be managed by undoing the hose coupling to the thermostat housing, losing some coolant despite bungs at the ready and using a screwdriver bit with a small spanner as nothing else would fit in the space. There was an annoying cable clamp in the way too. After a bit of fiddling I got the old one off and was pleased to see the slip rings hardly worn. Chances were it was just the regulator at fault.

All back together now and sure enough the alternator charges nicely. Phew :)

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#4 ·
My battery maybe down on capacity I suspect but the main fault was certainly the alternator as it wasn't charging.
 
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#7 ·
Hi John-H,

1.8 TT 8N 2002 Quattro Coupe

I read your two hairy journeys and your details of how to repair the no charging issue. I had (well technically still have) the same problem.

Your post helped me a great deal, pretty much saved me a lot of cash as well, as I presumed it would have to be another alternator. The alternator was fitted just 4 weeks ago (new) as the garage I bought it from on their way to delivering the car the battery light came on!

I didn't take it back regards the alternator failing after 4 weeks, as they had the car back again during the 4 weeks guarantee cover. Not bad I thought for a small family run business. They fitted a new turbo to the car! Not a cheap item and I'm fairly sure that would have all but wiped out their profit!

The problem with my regulator was one of the brushes had jammed up inside the plastic housing.

So I have the regulator out, and have another enroute. Yes, it was difficult to get the screws out, especially as you can't see them. But knowing it was going to be like that helped.

So, the bottom line is simply.......Thank you for your post. :D
 
#8 ·
And it's a timely post at that!

Just managed to get home myself a few minutes ago, all was well then suddenly the dash lights up and the battery warning light beeps at me. Luckily I was nearly home so made it ok but battery completely flat as soon as I turned of the ignition. I can see the belt is still there (and I've not heard it slip) so assumed the alternator was dead.
How can I diagnose if it's the alternator or the regulator?
Up till now it's been starting first time every time even in the mornings when it's minus 4 so I know the battery is good..
 
#10 ·
As per Hoggy's reply ^^^

There is good advice regarding the voltage regulator (VR), fuses to check and battery connection checks etc.

If you have access to a multi-meter, check the voltage from the battery without the engine on. My fairly recent battery reads 12.75 volts.

With engine running at idle, check the voltage from the battery again.

It should read above 14 volts which would suggest that the alternator is giving the battery charge.

If there is no change from your initial reading (or possibly lower) with the engine running then it would probably be alternator related.

The Bosch VR is an easy fit/repair item if undertaken by someone who knows what they are doing.

If the charge while your engine is running is OK, then you might have a battery drain issue. This could be attributed to a depleted/corroded battery in the alarm or even down to an after market radio head unit.

Hope this helps a little.
 
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#12 ·
It can be very stressful having your alternator fail. It needs to work each journey otherwise you won't have a next one! The fix is not so hard usually it seems as the regulator is often the problem. A multimeter is certainly your friend on these occasions - 14V indicates a working alternator but under 12V and it's going flat.
 
#14 ·
It was a hairy episode but like you say, you make your own luck - when there's a will or enough desperation :wink:
 
#15 ·
Enjoyed reading this; thank you for posting it. Good to know what to do, if this happens to my car (should that be when!?)

I have an alternator/battery tester; given to me years ago by a customer of mine, who was a retired mechanic.

(Similar still available on eBay; Item number 291534070121 at ÂŁ15.99)

Not only does it measure the charging voltage, but you then stop the engine and use it to place a discharge test on the battery.

If you use it when servicing etc. you can anticipate a dying battery.

Mine is analogue, with a needle type gauge, others are now digital.

"Knowledge is power" Thanks for some of yours! :p

Regards,

Specsman. [smiley=toff.gif]
 
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#16 ·
Trickle charged the battery last night, read 12.5 on the multimeter this morning and started on the button. However it's definitely not charging since it quickly dropped to 11.3. As suggested by the Hoggster I checked the fuse which was fine.
Since the alternator has been fine (not noisy) up till now my guess would also be the VR.
Is it a pita to fit? Or can I do it outside today? I replaced plenty of other parts on this car so I'm sure I can manage it. Just don't know where it is :oops:
 
#17 ·
Here's a picture. This is with the cover and plate in front of the orange dip stick removed (see my thermostat How To), showing the alternator with plug and output lead detached. You can see there's not much room:

Image
 
#18 ·
You're right about the lack of room, this job is a x10 on the expletives scale [smiley=argue.gif]

For anyone else who's attempting this without removing the hose it's a pita!

This is the 8mm bottom bolt which is hard to reach because of the hose & dipstick tube (which I removed)
Image


And here's the Phillips screw which is also very awkward!
Image


Reaching the top two bolts is ok (13 & 15mm) the lower bolt and screw are tricky. I should mention that the pictures are not orientated correctly.
 
#22 ·
No idea. I'd only trust a genuine Bosch part and not a Chinese copy. You don't want it to fail and have to repeat the job. You might be able to get one from GSF at half the dealer price or TPS is another possibility for genuine items.
 
#23 ·
John-H said:
No idea. I'd only trust a genuine Bosch part and not a Chinese copy. You don't want it to fail and have to repeat the job. You might be able to get one from GSF at half the dealer price or TPS is another possibility for genuine items.
Click to expand...
I thought about that and decided its the right thing to do. Its not a job I want to do twice put it that way!
Called Taunton Audi who will have the part for me on Tuesday which is a bit of pain but I have another vehicle so not the end of the world.

Interestingly (or so I thought) the VR is sold on a part exchange basis? Not sure what Audi would do with the old one? If I was buying the entire alternator that would make more sense to me...
 
#24 ·
At the risk of boring everybody...well anyone who follows this thread :wink:

Update to say that I had to remove the hose and drain some coolant, it's almost impossible to reach the bottom screw with it in the way. I also finally managed to remove the two screws holding in the VR. The one nearest the slam panel is easy, but the other one less so!
The good news is that after removing the VR I can see that the slip rings are worn but not terminally so that's a relief.

I'll add some more pictures at some point, it might help anyone else who attempts this.
 
#25 ·
Just a thought; from someone who has never done this repair...........

Is the alternator so difficult to remove? Then it would obviously be easier to split, from the vr, on the bench. :?

When I needed to do my thermostat, I was watching YouTube videos to get a feel for the job; and at least one advised removal of the alternator.

Regards,

Specsman [smiley=toff.gif]
 
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#26 ·
SPECSMAN said:
Just a thought; from someone who has never done this repair...........

Is the alternator so difficult to remove? Then it would obviously be easier to split, from the vr, on the bench. :?

When I needed to do my thermostat, I was watching YouTube videos to get a feel for the job; and at least one advised removal of the alternator.

Regards,

Specsman [smiley=toff.gif]
Click to expand...
I assumed it was easier not to, but I'm sure someone can advise on this? I'm also quite stubborn, so once I'd decided to do it in situ that was it!
 
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