The BSA A7-A10 Forum
Technical (Descriptive Topic Titles - Stay on Topic) => Lucas, Ignition, Charging, Electrical => Topic started by: bakerlonglegs on 22.08. 2021 12:42
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My A10 1953 plunger is my first Brit bike and my first anything with an ammeter. Because of that I don’t know what the ammeter indications are supposed to look like! *dunno*
I’ve fitted a DVR2 regulator to the bike. I charged the batteries before fitting.
When I turn the little running light on the ammeter drops a segment towards the negative. With headlight on it drops two segments. With the lights off the needle stays in the middle and doesn’t move, regardless of revs. Have I got a charging problem? What’s the ammeter supposed to do? Sorry, I know this is a really muppet question!
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With the headlight on, ammeter should show a discharge (as yours does) with engine stopped or running slowly. Increasing revs should bring needle back to centre - or slightly the other way if battery needs charge as well as powering lights.
PS - there's no muppet questions, only sometimes daft answers.
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The ammeter showing a drop with lights on shows that the lights are correctly connected vs the battery & ammeter (the battery supply goes through the ammeter then to the lights), but should only occur at idle and engine off.
No positive charge showing on ammeter with some engine revs, possible causes : battery fully charged, a defect in charging system\generator, wrong wiring.
Got a voltage\ohm multimeter? With engine running check if the voltage at the battery increases vs engine not running. If no increase something is wrong. Start with a check against the wiring diagram https://www.a7a10.net/forum/index.php?topic=8138.0
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With the headlight on, ammeter should show a discharge (as yours does) with engine stopped or running slowly. Increasing revs should bring needle back to centre - or slightly the other way if battery needs charge as well as powering lights.
Pay attention to Mr RDfella!
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Point your bike at a wall, turn on the headlight. If it gets brighter as you rev it above tickover, your charging system is OK but your ammeter wiring isn't. If it doesn't get brighter, you have a charging problem.
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Thank you very much for your replies! Right, back out clutching my multimeter, results:
Engine off, lights off is 6.4v (all at the battery), needle in the centre
Engine on, lights off is 6.4v, needle in the centre, no needle movement
Engine off, lights on is 6.04v, needle just above far negative of scale
Engine on, lights on is 6.04v, needle just above far negative of scale, no needle movement
Engine was at a fast idle.
But this is with the batteries recently charged and toddling up and down the little road where I live.
I will check the wiring connections. Lights, stop light, and horn all work properly.
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Point your bike at a wall, turn on the headlight. If it gets brighter as you rev it above tickover, your charging system is OK but your ammeter wiring isn't. If it doesn't get brighter, you have a charging problem.
Just read this, will try it now. Thanks!
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Tried that, the headlight doesn’t get any brighter, looks like a charging problem then. Thanks for the diagnosis advice!
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Could be that your dynamo just needs "flashing". Take a wire from the non earth side of battery and momentarily touch the field connection on the dynamo a few times with the engine stopped. This should re-magnetise the dynamo.
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I have the same problem. I have checked the dynamo output by connecting F & D together and putting an analogue meter to earth. It shows 10/12 volts with the engine running ( 1500/2000 rpm).
If I connect the green and yellow wires from F & D to the DVR2 regulator, which is new, and meter the brown/white (which are connected together for 6v operation) and the black output wire I get less than 0.4 volts.
I sent the regulator back as faulty but Mike told me its is fine. Its now fitted but still no meaningful output. What am I doing wrong ??
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With F and D connected you should get much more than 10 -12 Volts. Remove the dynamo (for better access) check the condition of brushes and commutator. First make sure the brushes are not worn down to far and that they move freely in their holders. Clean the commutator and make sure the gaps are not clogged up with carbon dust. Incidentally even if the battery is fully charged when you blip the throttle the ammeter pointer should still kick over to the charge side when you do so. The DVR2 is a brilliant piece of kit and in service works well, and is very reliable. Double check all your connections especially ground connections.
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With F and D connected you should get much more than 10 -12 Volts. Remove the dynamo (for better access) check the condition of brushes and commutator. First make sure the brushes are not worn down to far and that they move freely in their holders. Clean the commutator and make sure the gaps are not clogged up with carbon dust. Incidentally even if the battery is fully charged when you blip the throttle the ammeter pointer should still kick over to the charge side when you do so. The DVR2 is a brilliant piece of kit and in service works well, and is very reliable. Double check all your connections especially ground connections.
+1 for all of that.
When you've cleaned things up etc, suggest testing the dynamo with a load hooked on when it's running ( a mains-powered drill will be fine for driving it), to see if you still have any volts showing. A 12v bulb of reasonable wattage will usually work well.
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I’m still battling with this non charging issue!
I’ve tried testing the dynamo by connecting the F and D together, starting the bike, connecting the positive wire of a voltmeter to a terminal then the negative to the engine. The voltmeter comes straight down to around minus 10v when the engine is running. *dunno* Have I done that right? Would that account for why the ammeter doesn’t show as charging? It’s a positive earth 6v bike.
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Did you polarise the dynamo as advised?
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Did you polarise the dynamo as advised?
Yes, good question - I have tried that, got good sparks as I touched the terminal.
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It is positive earth so the positive probe should be connected to earth to get the correct polarity reading.
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Hi All.
Do not rely on a voltmeter when checking dynamo output...
Connect D an F together and onto one side of a 12v headlamp bulb, and connect the other side to the dynamo body,
Start the engine or mains drill and spin the dynamo in the driven direction.
The bulb should light and brighten with more revs if all is good..
Battery drills are not fast enough to fire up the dynamo..
If the dynamo is off the bike, connect a battery in place of the bulb, D+F and dump body.. the dynamo should motor in the driven direction.. if it turns the opposite direction, swop either the field or brush connections. Not both *ex*
John
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Another variable is direction of rotation.
It is reversed by swapping either the brush connections or the field coil connections.
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Thank you all for your replies!
It is positive earth so the positive probe should be connected to earth to get the correct polarity reading.
Oh! That makes sense. The dynamo is working then. Time to recheck connections and the DVR2.