I just got my 1963 Atlas with magneto back on the road and having some trouble with the electrics. I converted to 12V with a Podtronics rectifier/regulator and fitted new RM21 stator, rotor, battery, PRS8 and new Lucas wiring harness. One of the two alternator cable goes into GN/YLW and the other into a combined GN/WH and GN/BLK, see attached wiring diagram. The alternator is working fine, when testing with light + capacitor. I get a DC output from the Podtronics box, (pos.) earth connections seem fine. However if running with the lights on, the Ammeter shows the same discharge as when off. All lights and switches are working as they should. Have I missed a connection? Anything to check with light or multimeter? Any hints and suggestions much appreciated!
thanks, Holger
Does the ammeter show a…
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The ammeter is moving and…
The ammeter is moving and working, checked with a battery. The meter is giving me 12.6v at the battery and again 12.6v with engine running (both idling and at c. 3,000revs), then drops to 12.0v as soon as the lights are switched on. So definitely nothing arriving at the battery!
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Yes no charging from the POD…
Yes no charging from the POD, so the POD is defective or there is a fault in the wiring so no charge is getting to the battery.
Next test is removing the 2 wires from the ammeter and connecting them together with bare ends taped over to prevent shorts. That is the only connection between the brown/white wire at the POD and the brown blue wire at the battery so bypassing the ammeter will show if its the issue.
Do the same voltage tests at the battery.
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Do not
Do not...use a cheap Digital meter to check this voltage. They pick up ignition interference and read 'any old thing'. Use a specific Auto multimeter or a traditional analogue meter. Do not be obsessed with the actual voltage, it is the rise of about 2v that is important.
Ammeters on motorcycles can easily be missed wired in that they reveal the discharge but fail to read the charge which is actually occurring. (oh yes they can!) The real test of charge is the rising voltage,
The wording by Holger in this POST is actually wrong,with regard the alternator wires that feed the reg/rect. But the diagram is correct. By the way the real Lucas demised in the mid 1980s. This is a far East product brought about by Wassell-no technical back up. And despite it have a Zener connection it is initially a 6V loom.
I can test the Podtronics reg/rect if you send it to me with some return postage. But an easy test of it is remove it, replace with a traditional bridge rectifier, start engine and note charge voltage. DO NOT go for a ride unless you keep your lights on to save over charging the battery. But this will confirm/deny the Podtronic.
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Sorted! Thanks for all the…
Sorted! Thanks for all the advice! Checked voltage on the DC side of the Pod with a meter (an automotive one!) + resistor and it was fine, rising ok with revs, but no current increase when the meter was inline with the live wire with the lights on. Turned out to be my wiring mistake at the PRS8 switch, one of the BRN/WH wires ending up in pos 7 not pos 3, which should have both BRN/WHs on the switch.
Btw, the ‘62/63’ magneto model wiring diagram in the handbook shows a rectifier cable going to pos 7. I can’t figure out what it actually does there as it would only connect to the direct alternator output when the switch is in the off position. Wouldn’t that somehow combine an AC feed with a DC wire when the engine is running? For what purpose? Some coil ignition models had an emergency position, but that wouldn’t apply to magneto systems.
Thanks again for the help,
Holger
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With out...
Without looking at the PRS8 I would agree that in certain cases the PRS8 would switch in emergency ignition by putting the AC direct to the ignition coil. Nasty but it gets the engine running, and it does say to switch straight over to Battery.
But even though you don't need such with a magneto, why has a Magneto bike got a PRS8 switch?? As far as I know the Atlas never had a PRS8.The Atlas was always 12V but I am open to 'argument' on this point.
The other function in the PRS8 which is redundant is the switching out of the rectifier when the ignition is off (due to leaky old Selenium rectifiers).
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Does the ammeter show a discharge all the time or will the needle move, it could be just stuck, never had one that worked for long.
Connect a muti meter set to volts onto the battery, note the volt reading, start the engine and note the voltage when the engine is idling and also when being revved. Now with the engine still running turn on the lights, note the volts at idle and when being revved.