205 Dying

[scott-205gti 2]

Can anyone explain a method to distinguish  between an Alternator or Battery fault  ? My 205 died on the way home .Could not restart the engine .Once I got it home I recharged the battery and put it back on the car . It started with no problem and ran happily  .Without the car running it had about 12 volts across it .Once the engine was running this was about 11.7 volts .This with the lights on .I would have thought it should be 14 volts approx ? Does the low voltage confirm an Alternator fault ? Or could it be the battery ? I would be grateful for any help on the subject .Its just I don,t  want to blow money on the wrong proble

[chris205gtioliver 0]

I'm not too sure but what are the volts when it's reving a bit higher? Does sound like the alternator at first glance though.

[Anthony 1,003]

Alternator related fault. As you said, you should be seeing around 14v with the engine running.

 

Does the alternator/battery light come on with the ignition, and go out when the engine starts as it should?

[scott-205gti 2]

Yes it does .

Alternator related fault. As you said, you should be seeing around 14v with the engine running.

 

Does the alternator/battery light come on with the ignition, and go out when the engine starts as it should?

[Anthony 1,003]

I'd say that the alternator is goosed them I'm afraid, as if the light is working that rules out that being an issue to stop the alternator initially charging.

[scott-205gti 2]

Hi i have just fitted a second hand alternator from the local scrap yard and has made no difference at all. Admittedly it could also be faulty, so because father has a 205 gti i was going to connect the alternator from his 205 to mine via a length of cable. And see if this does the trick. I also noticed that there is a current of approximatley 5A flowing into the car with the ignition turned off and all fuses and relays removed from the fuse box could anyone shed any light on this matter. Does anyone know how to trace or find the fault as its a concern ?.Thanks for the help so far.

[jeremy_spoke_in 2]

Check there is a good earth between gearbox and battery. I've been having charging problems and this was the fault. Just remove cable and clean with emery(spelling?) paper, reattach cable.

 

All lights came on dash as normal when key in ignition mode, but when trying to start the starter made no effort to spin. I put a length of cable betwen battery neg to starter motor and it seems problem solved.

[scott-205gti 2]

Hi i have tried a known good alternator and battery off my dads gti and still have the same problem and im also getting a negative voltage reading aswell, also there is still a current of 5A going somewhere with the igniton off is it possible that there is a short somewhere or a bad earth to the alternator, as i need the car to work quickly as i need it for college and it needs to be reliable as i need to cover 1500 miles.Thanks

[P_Monty 2]

Hmm 5A with ignition off and all fuses pulled is definitely bad ... The first place that sprang to mind for it to be going is the alternator - unless there's a 'bit of a short' at the starter ...

[scott-205gti 2]

I have got a bit further with the charging problem and realise one of my posts was in error .The situation is that on turning on the ignition there is no ignition / batt light and with the engine running still no light .The batt voltage ( measured across the battery ) is approximately 12 volts . I tried earthing the alternator directly to the battery and also connecting the alternator output to the battery .Still no differerence .I then swopped alternator and battery with my Dads GTI .His was running fine and showed a charge of 14 volts approx .But once fitted to mine still only 12 volts approx .Then I tested the small tag on the alternator on my Dads GTI and found 12 volts on it .On mine I there was zero volts .So out of desperation I connected the battery positive to the small tag on the alternator on my car and struck up the car .Now I have a healthy 14 volts on my battery .The Haynes manual indicated this was just a feed to the ignition / battery light so I ignored it until now . This seems to be more then just an light .Can anyone tell me what this is ? It seems it may be a voltage reference for the alternator .Where is it taking its supply from ? Would it be okay to leave the temporary fix in place ? Incidentally I put the original alternator on my dads car and started it up .It produced 13.5 volts at the battery .But removing the small tag on the alternator dropped the batt volts to around 12 volts .This seemed to indicate no charge again and confirmed this small feed has something to do with the problem .It also seemed to prove my alternator was fine .Thanks in advance for any help as its driving me nuts .

[P_Monty 2]

Thats the excitor wire for the alternator - basically as you've discovered, it causes the alternator to produce charge. I don't know if you'd noticed, but if you rev high enough (above about 3k I think) the alternator will self-excite and should put a decent number of volts on the battery.

You should also notice that with the tag connected properly, the light on the dash should come on. I don't know about leaving the temporary fix in place though ...

[scott-205gti 2]

I have now located the wire that goes to the alternator in the instrument panel .Testing for continuity there appears to be an open circuit somewhere . I then connected a wire between the Alternator small tag and the other end on the Instrument panel .The Ignition light did come on but very faint . It was then I realised that the other warning lights were dim . So I checked the voltage and found 6 volts approx on what the Haynes manual says is the pos supply to the Instrument panel .Therefore I checked back at the fuse ( which Haynes says is for the warning lights ) and found about 6 volts again .The only thing I can see between this and the battery is the actual Ignition switch itself . So I will change it as I found it did not cut the supply off completely and even with the key removed the warning lights were glowing dimly .I wonder now if this is where I was measuring a flow of current when I thought the Ignition was off ? Being daylight I had not really noticed before any illumination on the instrument panel .Hope this will sort it .Thanks for the help so far .

[P_Monty 2]

Sounds possible - if the ignition switch is fubarred then, it might well be giving a continual resistance at all times, rather than a clean on/off action...

[scott-205gti 2]

No the Ignition switch did not sort it out at all .I seem to be stuck with a permanent feed to the instrument lights e.tc .I removed the brown plug ( yellow & red wires ) on the switch and I still had a feed to the instruments e.t.c .Anyone know of any plugs that could possibly be reversed on the wiring loom that could cause this problem .I should add as I have not before ,that this car has had a 1.6 engine fitted in replacement of the 2.0 ltr MI16 .

[darrellspeed 1]

are the yellow earth plugs connected properly on the left hand side of the steering column?

[scott-205gti 2]

Hi thanks for the reply i have know sorted the problem turned out that the self exciting wire on the back of the alternator had an open circuit on it so a new wire was re-fed and so far touch wood i have had no problems after 130miles. Thanks scott