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+--- Thread: Strange charging symptoms (/showthread.php?tid=4933)
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Strange charging symptoms - 12jslater - 10-09-2020
Hello!
I've just been rewiring my Austin big seven, and I'm very confused at the lack of charge to battery, when I rev the engine the ignition lamp goes off, I have a happy 14.3 volts at the battery however when I switch on say the headlamps or another accessory the ammeter is reading a discharge with no difference when revving the engine despite the ignition lamp being off.
I'm baffled as to what it could be
RE: Strange charging symptoms - Ian McGowan - 10-09-2020
What you haven't told us is the ammeter reading when you are observing your "happy 14.3 volts"??
RE: Strange charging symptoms - 12jslater - 10-09-2020
No it's not reading any charge at all, it's just sat slightly towards discharge.
RE: Strange charging symptoms - Ian McGowan - 10-09-2020
thank you, I would suggest that maybe you have the dynamo output connected to the "wrong" side of the ammeter i.e. the battery side. If this is so any charging current to the battery would not be indicated on the ammeter.
RE: Strange charging symptoms - bob46320 - 10-09-2020
Have you "flashed" your dynamo to regain its residual magnetism - Frowned upon but can work.
RE: Strange charging symptoms - 12jslater - 10-09-2020
The dynamo has been flashed and the ammeter is wired the correct way as when the headlamps are switched on without the engine running it measures a discharge, same for wiper motor, brake lights etc.
I'm puzzled by it
RE: Strange charging symptoms - Ian McGowan - 10-09-2020
I still believe that you may have the dynamo output wired to the wrong side of the ammeter (via the cutout/ regulator). It should go to the opposite side of the ammeter from the battery and starter motor, putting it another way round, it should go to the same side as the lights , accessories etc. See wiring diagram below.
http://www.austin7.org/Data%20Pages/Big%20Seven%205/
Everything that you have said indicates this. The dynamo is obviously charging the battery - hence your "happy 14.3 volts", but NOT via the ammeter.
RE: Strange charging symptoms - Bill Dixon - 10-09-2020
From memory the lead from the battery to the ammeter is black/yellow,the lead from the "A" post on the control box to the ammeter is purple/white. If you have the purple/white connected to the same tag as the black/yellow then you will have the reading as Ian G has said. Suggest you check.
RE: Strange charging symptoms - 12jslater - 10-09-2020
Finally got the ammeter to read correctly, however now I have the issue of when I rev the engine the ammeter jumps straight up to full charge...
RE: Strange charging symptoms - David Stepney - 10-09-2020
Sounds as if the third brush which controls the dynamo output needs adjusting. If memory serves me aright, moving it in the direction of dynamo rotation decreases the maximum output, but I stand to be corrected in this.