Battery light not going out.
 

i have posted this on Facebook too to see if anyone can shed some light:-

I have a '82 Coupe GT 5s, when I start the engine the battery light stays on normally for a while (not sure if right for this age of car) on that day but every start after that goes out fairly quickly (about a minute or so) and the voltage on the volt meter from about 11v to 13v ish. The other day the battery light did not go out and the battery went flat on a drive.
I have changed the alternator for a different one and put a meter on the battery and voltage does go up when engine is running but battery light stays on and VDO gauge does not agree with meter directly on battery. Is there some relay that is playing up somewhere? Is there some checks I can do to see what is not working? Have also wondered if it is worth running a ground lead directly from the body of the alternator to the -ve of the battery?
I look forward to any help.

I am no expert on alternators, but if the light is on the battery is not charging, you original alternator sounds like the carbon brushes have worn out, this dose happen with old cars and old alternators, you can normally replace the carbon brushes but the norm is they come attached to the voltage regulator, the voltage regulator is normally at the back of the alternator fixed in with 1 or 2 screws, a we bit tricky job to do on the car but can be done as I have done it on the Ur quattro, after fixing the the Ur quattro voltage problem I did order a spare voltage regulator as one of my other cars has the same alternator, photo below of spare voltage regulator, this may not be the exact same part as yours but may be similar, the two carbon brushes are at the top of the photo and are on springs, yours will be a lot shorter as the springs push the brushes against the alternator shaft and they wear till they lose contact and battery dose not charge, as for cost £10-£20, no comment to make on you second alternator problems.

https://i.imgur.com/uTnyBvC.jpg

Sounds like the replacement alternator is faulty? If you remove/disconnect the small wire from the alternator and the light goes out then alternator has an issue. If light stays on then suspect wiring or problem behind clocks/dash.
If engine cranks ok then I'd not worry about adding a separate earth lead, just make sure the alternator is secure and earthed to bracket/engine.

Does the B2 have a flashing oil warning light like mk1 Golf?

Morning John, very nice reply, with wire testing, need to keep that test in my mind but will need to push some other crap out, but what to push out Hmmm, Sorry, I have had 3 cups of coffee and can't stop typing, Have a nice day.

I NEED 3 cups of coffee !

Are you sure the alternator you put on works ? you post suggests it's not new ?

Hi guys,

Thank you for your replies, I will try and answer all you points.

Colin - Changed that on the old alternator and no difference

John - With the D+ wire connected or disconnected the light stays on.

I have been told by someone else there should be a voltage between the lead that goes to D+ and ground but when I put a meter over it I get 0v with ignition off and 0.05v with ignition on. So I am guessing that is the problem - if so does that track back to a relay or what?

Sounds like you have a problem that isn't the alternator.........I was asking about the oil light as I remember on mk1(and maybe mk2?) Golfs that there's some electronic trickery built into the dash clocks?......maybe this could be your problem.....I don't know how you'd test this, probably easier to install a set of clocks that are known to be good?

Maybe worth-while checking all connections and earth points around dash area as it could just be that another circuit is earthing itself via the battery ind circuit??

:hmmm:

I guess I know what I am going to be doing for the next few nights now:wall::wall::wall:

Just hope I find it quickly, wish me luck :tup::tup:

Well, first of all - you say that "multimeter on battery doesn't match reading of VDO voltmeter" - what's the reading of both? If gauge shows some quarter volt below voltage on battery, that's normal, as there is some voltage drop between battery and gauge. The only question is - how good is your alternator working?

If you can remove exciter wire from alternator, and alternator light keeps shining, apparently exciter wire is grounded somewhere - but alternator self-excites if it's being revved behind some threshold; let's say, if engine is revved past 3k rpm - just for your info, if you continue to drive the car without this problem being solved.

As for "electronic trickery" John is speaking about - in order to rule that out, you can remove oil pressure warning relay - in VW's it's in cluster itself, but in audis of this age it's separate relay, must be above drivers feet [at least in LHD cars], with "õl druck kontrolgerāt" written on it, if you remove it, that removes oil pressure warning [both buzzer and light], but if that restores normal behavior of battery light, you'rs is faulty.

When doing the last test the VDO read about 11.5v and the meter was 15.2v - I know when the battery light goes out the VDO normally goes up to about 13v

That was what I had to do on the old alternator, but had to hold rpm above about 4k and sometimes red line it after driving for about 3 to 4 minutes - used to get funny looks driving along doing that.

I have a relay behind the dash and always wondered what what was for, I do not have a buzzer as far as I know but do have the oil light flash while the battery light is on. I will also check that.

Here is the back of the dash:-
http://www.classic-audi.co.uk/forum/...pictureid=8987

I have done a continuity test between the end of the lead that connects to D+ on the alternator and the end that connects to the dash to light the battery light - all good. Done a continuity test between lead and -VE on battery with neither end connected and from both ends reads that is connected to -ve no resistance. Same and to +ve and depending which way meter is connected either 456 or 1156 and climbing.

Pulled out the electronic relay that is top right in the dash and the oil warning light want out but the battery light stayed on.

So, tell me if I am wrong, there seems to be a problem in the fuse box. If so what could the problem be?

This is really starting to stress me now.

There's no problem in fuse box, as the only possible problem would be blown instrument cluster supply fuse, in which case everything electric apart from clock would be dead in cluster.

I asked you to remove oil pressure control relay and drive the car - obviously with engine not running that relay cannot affect alternator light in any way, as it's connected to exciter wire solely for it's own needs to help it determine if the engine is turning or not.

I will try and find that one, I thought is was one of the 2 on the back of the dash but one is the gear up relay(171 919 091a) and the other (not sure if this is the one you mean) turn the flashing oil warning light off (433 953 213b). Pulled both those and revved the engine hard (upto 5k plus) and not difference to the battery light going out.

Is the car a daily driver?....if yes just start the engine and earth a bulb to the IND terminal on the alternator and it will start charging the battery.........means you can use the car?

I use it regularly but not daily, when you say IND terminal I assume that is the D+ terminal. At least I will feel more comfortable using the car knowing it is charging while I am sorting problem correctly.

Well, I have no idea how you have figured that out, but that's not gonna work. For alternator to start to work upon starting to turn, voltage regulator must be provided with positive voltage on exciter wire - that could be achieved by connecting exciter terminal and alternator output terminal, but that would end up in draining the battery when engine is off.

I was thinking that when I read it which is why I had to check. If I connect the D+ temporary when I want do drive the car for now while trying to suss the problem this will be OK wont it?

Temporary solution is not touching anything and revving engine high enough so that alternator would self-excite, after starting the engine. I once had to do that - I was piloting my neighbours T4 2.4D with wire between alternator and indicator light broken - after we found out that the battery is flat and we had to push start the car, I figured out what is wrong, so for the rest of the ride after engine being stopped and restarted, I started with harder acceleration in first gear.

If your alternator doesn't respond instantly when not charging and engine being revved to 4-5k - I would suggest to inspect the alternator...

All I would do is earth the side-light bulb(side that's closest to alternator) via the IND/D+ terminal on the alternator.
Start the engine, switch the lights on and this will do the job of the dash bulb. After you've done this the alternator will be charging......you can turn the lights off again but beware if you actually need to use the lights then the sidelight won't work!
Simples !

If you don't need that bulb be illuminated, you can do like that :D If the ground pin will be connected to alternator, that bulb will work like alternator light should - it will be illuminated when alternator won't be working and it will go out after alternator will start to work.

I know you and I understand but not sure the OP does?
I described it as such so the bonnet wouldn't have to opened every time the engine was started.:tup:

...or engine revved...

If I would have such a problem, I wouldn't bother and would rev the engine, as connecting alternator to some bulb - that's too much effort for lazy arse like me... :lol:

I am going to try that today, also read somewhere something about linking it to the oil press switch. Is this correct?

Not found the relay yet you mentioned, unless it is the one in the dash I have pulled that made no difference.

On a "normal" set up this would work, as yours has the flashing light/relay set up and there's a chance the problem is with dash(?) then maybe it wouldn't work? I don't know is my honest answer............MSH !

Latest update.....

A little confused:crazy::crazy: but that is nothing new for me. Have been getting stressed with this issue and especially as I could not work out the relay I had to pull...... so.... looked at the fuse box and disconnect loads of bits, and reconnected just what I needed to get car running and replace afew connectors, and...... well started car battery light on still with flashing temperature light still. Touch the accelerator and the lights go out and VDO reads a happy 13.5v Carried on reconnecting things and making sure they are where they make sense being and well just done a 12 mile drive and car feels sweet.

Thank you guys for putting up with me :tup::tup:

Sounds like a good result :)