Me and My Christmas Alternator (A4 B5 2.8 Quattro)

[stoocake]

Hi all, I'm new to Audi, and so this forum.

First things first - Merry Christmas!! Hope everyone has a good day ahead of them.

Sorry if this is in the wrong section - wee bit desperate for help.

Onto the car - I just got an Audi A4 Estate. It's a 1998 Model, 2.8 Quattro Automatic.

I've been using it the last few days, but Thursay night on my way home the alternator light came on after pulling away from the junction. I built the revs up to around 4,500rpm, after which the battery light on the dash illuminated (and volt-meter dropped to 12v from a usual 14v). I was only a minute from home so made it back, and the car appeared to be running ok.

Friday morning I tried the engine again and battery light had gone out, so set off for work. Made it most of the way there and it came back on. Same again on the way home.

I've been under the car and had a look - earth from alternator to chassis rail looks ok, given it a wee clean up just in case. Getting a steady 15.5v shown on multimeter at battery terminals with the engine both on and off, but dashboard showing less than 12v so I'm guessing that that reads from a different source?

I just thought I'd ask here to see if anyone can give me some pointers on what to look for. If it's an alt-out job, it's going to be a right git to get out. Especially on Xmas day as otherwise I'm stranded home on my own

Battery Voltage with engine running and no Alternator light: 17.85v
Battery Voltage with engine running and Alternator light on: 14.65v
Battery Voltage with engine not running 16.28v

Sorry for long post, hopefully someone can help.

[martin mrt]

It looks as if it's overcharging

[stoocake]

The numbers are very high when the battery light isn't illuminated I suppose - do you think this points to the voltage regulator on the Alternator then?

[HD Adam]

I would check your voltmeter mate. The readings are too high.

Anyway, its an alternator out job. If the light has just started to come on intermittently, it's probably the brushes.

[stoocake]

I should probably change it's battery, I've had it a while. Cheers.

Thanks for the heads up - never done much work on electrical systems before...I'm more a steel and oil kinda guy.

Does anyone know if it is in fact a front-end off job to get to the alt? Space is pretty damn tight as it is but thanks to the snow and lack of garage, I've not jacked it up for a proper look.

[Larry Dickman]

stoocake said:

The numbers are very high when the battery light isn't illuminated I suppose - do you think this points to the voltage regulator on the Alternator then?

This is what I'm thinking because with the engine running with the alt light on your volts are closer to what they should be, but it probably isn't charging. So maybe your regulator has been over charging for a while & now the alt has started not charging altogether you've discovered the original problem.

You may be able to change just the regulator & brushes in the alt with out removing it from the car, & also will be a lot cheaper.

Try here http://www.woodauto.com/Component.aspx?Ref=VRG4651... you'll need the number from the old one & go into vehicle lookup or search maybe.

ETA.. After reading HP Adam's post I think he may be right. Your battery shouldn't be chucking out that much voltage at all so maybe just the brushes, although they come with a regulator anyway.

Edited by Larry Dickman on Saturday 25th December 14:11

[RV8]

You can replace the regulator if you are lucky this might be the issue as these can be quite cheap. The lucas alternators (and equivalent) regulators are less than a ten quid usually and are quite easy to fit if you can get access the alternator. You have to be gentle fitting them so you don't damage the brushes. Mine was charging on tick-over but undercharging with revs which seems daft but they can throw up some odd scenarios or the alternator can give up the ghost, or the brushes can wear out.

You could replace the battery too if you think it's on the way out but I'd be inclined to believe that the fault is with the alternator or more likely the regulator. I'd rather be confident that I have a working alternator before forking out for an expensive battery as replacing the alternator sorted me out where as a new battery would have temporarily hidden the undercharging issue (which was the opposite problem to yours). May as well chuck a new 'fan' belt on there too while you are at it.

Hope this helps, Merry Christmas.

[stoocake]

Thank you so much for the replies, I really appreciate people taking the time out of their Christmas day to help

Hopefully I can pop the regulator/brushes out with the alt in situ but access is tight and visibility even more so. I expect the easiest way to get the alternator out is to remove the radiator, but I'll keep this thread updated should it help anyone in the future.

Hope I get it going! Loved driving it for the 2 days I've had it

[Pigeon]

stoocake said:

Getting a steady 15.5v shown on multimeter at battery terminals with the engine both on and off

Battery Voltage with engine not running 16.28v

Your multimeter is buggered, there's no way you'll get that high a voltage with the engine off. You need to sort that out before you can do any useful fault-finding with it.