Battery light not going out.

[krzracingcouk]

Originally Posted by msh

what's the reading of both?

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

Originally Posted by msh

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.

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.

Originally Posted by msh

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.

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.

[krzracingcouk]

Here is the back of the dash:-


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.

[msh]

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.

[krzracingcouk]

Originally Posted by msh

I asked you to remove oil pressure control relay and drive the car

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.

[John.]

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?

[krzracingcouk]

Originally Posted by John.

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.

[msh]

Originally Posted by John.

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?

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.

[krzracingcouk]

Originally Posted by msh

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?

[msh]

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...

[John.]

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 !