Author Topic: BSA plunger 500, lucas dynamo not working  (Read 481 times)

Offline vittoriobravo

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BSA plunger 500, lucas dynamo not working
« on: 17.03. 2015 01:40 »
Hello All,
its taken me years to get this bike up and working from a basket. now im trying to get the electrics working.
getting no voltage out of the two terminals of the dynamo when joined together with a voltmeter to earth when i start the bike.
is there an other easy way to  determine the fault.

regards
Vitto

Online Triton Thrasher

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Re: BSA plunger 500, lucas dynamo not working
« Reply #1 on: 17.03. 2015 06:40 »
Do that same test again and briefly connect battery live to D and F, while the engine is running at faster than idle.

Offline vittoriobravo

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Re: BSA plunger 500, lucas dynamo not working
« Reply #2 on: 17.03. 2015 09:17 »
thanks for the reply, is there another way of testing the dynamo  my battery dead, need a new one. thanks in advance.

Offline duTch

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Re: BSA plunger 500, lucas dynamo not working
« Reply #3 on: 17.03. 2015 09:30 »

 Yeah Vitto, do as TT said and join the 'D' and 'F' together and connect to one side of a volt meter, and the other side of the volt meter to earth and see what you have...or connect everything as per normal and add a volt meter to the battery....
....I have a battery that shows 2.2V in situ on a volt meter semi permanent connected to terminals, but when I start up it goes to ~7.*&*&^R%^$*$ volts *eek*....just have other things to check before I blow up another battery
 
 
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Online morris

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Re: BSA plunger 500, lucas dynamo not working
« Reply #4 on: 17.03. 2015 21:57 »
An easy test is to measure continuity on the field coil. Resistance should be around 2,8 ohms. If not it's probably short circuiting or broken internally. Also measure between coil and dynamo body. If you have a reading there, its isolation broke up and the coil wires are touching the dynamo body. In both cases the field coil is shot.
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