BSA c15 wiring problem

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star15
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Joined: Sun Oct 11, 2009 6:48 pm

BSA c15 wiring problem

Unread post by star15 » Mon Nov 10, 2014 8:26 pm

After fitting a new harness to a 1959 c15, + earth, as soon as I try to connect the red + wire to the battery the ammeter flicks up fully to the + side, The other wire has been connected to the battry, I have not fixed it to the battery as it starts to get warm, all this and the ignition switch is not even switched on. The lights work without the ignition switched on as it should be as I have one myself, I am doing this one for a mate, if I disconect the brown and white wires from the rectfier it stops, does this point to something faulty or have I got something wrong, will continue to Investigate.

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DAM
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Re: BSA c15 wiring problem

Unread post by DAM » Mon Nov 10, 2014 9:35 pm

You have one of 3 things wrong -

A faulty bridge rectifier.
A bridge rectifier for - earth.
Or you have it wired wrong.

If it is + earth you have the ammeter wired the wrong way round too.

While you are trying to fault find stick a car headlight bulb in line with one of the battery leads to limit the current.
Then when you have found the problem add a fuse to protect the wiring if anything else goes wrong in the future, it's a lot cheaper than a new wiring harness.

star15
Posts: 56
Joined: Sun Oct 11, 2009 6:48 pm

Re: BSA c15 wiring problem

Unread post by star15 » Thu Nov 13, 2014 8:56 pm

First the daft bit, the ampmeter, because the bike is + earth I put the red lead to the -, wrong way. So it was going straight to earth,I had two wires wrong in the headlamp, also when I pushed the fitting on the lightswitch right up it did not work right, pulled it down a bit, better contact, the only other problem, the pattern handlebar, high/low/horn switch had a short through it, this I insulated with some rubber. It seems ok now, just needs timed up, see if it will start up. Thanks DAM for clues, also pays to check wiring diagram.

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johnr
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Re: BSA c15 wiring problem

Unread post by johnr » Fri Nov 14, 2014 5:08 am

good little thing the c15. ive got one with a triumph piston in it which boosts the compression and capacity. its now somewhere round 270cc and picks its feet up like no c15 roadbike has a right to!

star15
Posts: 56
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Re: BSA c15 wiring problem

Unread post by star15 » Sat Nov 15, 2014 9:24 pm

Just noticed, I have one small problem, when I press the back brake,, the speedo light comes on,with the rear light, when the lights are on and i press the brake, the speedo light stayes on as it should, I have included a pic of the diagram, any ideas.
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c15_6volt_wiring_diagram.jpg

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DAM
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Location: North Cornwall

Re: BSA c15 wiring problem

Unread post by DAM » Sat Nov 15, 2014 10:26 pm

I expect you have the usual problem with the rear light, it's got a poor earth at the tail light.

Easiest way to cure it is to add an extra earth wire to the rear light.

star15
Posts: 56
Joined: Sun Oct 11, 2009 6:48 pm

Re: BSA c15 wiring problem

Unread post by star15 » Sat Nov 15, 2014 10:57 pm

I had already done that, the rear light and the speedo light are kind of linked undert the lighting switch, will keep looking, as it differs from my bike, dont know why as they are same year, must be slightly different harness.

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DAM
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Re: BSA c15 wiring problem

Unread post by DAM » Sun Nov 16, 2014 12:29 am

Is it an old tail lamp with signs of corrosion ?

It seems to me you still have a poor earth connection to the bulb. You could try substituting the rear light from your bike and see if the fault clears.

star15
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Joined: Sun Oct 11, 2009 6:48 pm

Re: BSA c15 wiring problem

Unread post by star15 » Fri Nov 21, 2014 8:17 pm

Thanks again DAM, I had already fitted an extra earth to the rear light, but I have traced the problem down to the new pattern rear light, if I move the bulb a little bit the speedo light goes off, so I think its a problem with loose wires inside or some earthing problem, will have a closer look, see if it can be sorted, or a fresh one fitted. Sorted today, one wire on the pattern rear light has the same colour that i used as an earth, changed over, now works as it should, the bulb moving has no effect now,I should have waited till i bought the new harness before wiring the rear light in, which i had done previous :D

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