Joined: Jul 2018 Posts: 102 Threads: 33
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10-09-2020, 11:46 AM
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
Joined: Aug 2017 Posts: 254 Threads: 3
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Location: Shropshire, UK
10-09-2020, 11:52 AM
(This post was last modified: 10-09-2020, 11:53 AM by Ian McGowan.)
What you haven't told us is the ammeter reading when you are observing your "happy 14.3 volts"??
Joined: Jul 2018 Posts: 102 Threads: 33
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No it's not reading any charge at all, it's just sat slightly towards discharge.
Joined: Aug 2017 Posts: 254 Threads: 3
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Location: Shropshire, UK
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.
Joined: Mar 2018 Posts: 682 Threads: 33
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Location: Lot region FRANCE
Have you "flashed" your dynamo to regain its residual magnetism - Frowned upon but can work.
Joined: Jul 2018 Posts: 102 Threads: 33
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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
Joined: Aug 2017 Posts: 177 Threads: 1
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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.
Joined: Jul 2018 Posts: 102 Threads: 33
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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...
Joined: Jan 2019 Posts: 1,481 Threads: 17
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Location: Bala North Wales
Car type: 1933 RP Standard Saloon
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.
