The BSA A7-A10 Forum
Technical (Descriptive Topic Titles - Stay on Topic) => Lucas, Ignition, Charging, Electrical => Topic started by: PaulC on 22.09. 2013 08:45
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Checked over my '59 Super Rocket yesterday and found brake light not working. Rear light is ok, but no brake light on pressing peddle. Changed bulb but it made no difference. Took the brake switch wires out and connected them together in case switch faulty - nothing. It was working fine the last time I checked and the only thing I've done to the electrics recently is to bridge the dynamo wires to check for output. Any ideas greatly appreciated.
This got me thinking. What is it, exactly, that makes the brake filament light up? Is the power to the rear light somehow suppressed and the brake peddle sends max 6 volts directly to the bulb? Funny how you take these things for granted until a problem arises.
Thanks for your help.
Paul
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What is it, exactly, that makes the brake filament light up? Is the power to the rear light somehow suppressed and the brake peddle sends max 6 volts directly to the bulb? Funny how you take these things for granted until a problem arises.
There's the clue above Paul
there should be two filaments in the rear light bulb one for rear light the other for the brake light (separate circuit - bigger wattage filament)
I'm guessing the brake light filament has blown
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G'day Paul.
I had that exact same problem with my A65 a month ago. Did the same as you and bypassed the switch but still no brake light (tail light OK). Power was getting to the fitting on both points but globe would only light the tail light. Tried 4 good bulbs, still no go. Pulled it all to bits and cleaned with electric contact cleaner and re assembled. Still no good so I gave it a backhander *bash* low and behold it started working. Must have been a bad earth or power was leaking to earth. We call it electrickery.
Cheers
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If it is a pattern rear light the bulb holders are usually very poor quality and often hit & miss whether they make contact with the bulb. I have sometimes rebuilt them using a bulb holder from a Japanese bike lamp.
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Thanks for your responses. I'll check it out at the weekend.
Paul
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Hi Paul, check the fittings for the mudguard to frame as thats the path where you'll earth the unit from and also the connection between the rear light unit and the mudguard ,same reason (with power being sent by the wire from mainswitch and brakelight switch . ) If that still doesn't work connect a wire to your battery earth lead long enough to each the light fitting and after exposeing a little bare wire touch it to bit of clean bare metal on the mudguard if the light works the mudguard is isolated from earth take the connections apart and clean so that everything is providing as easy a path as poss for the earth return. If nothing repeat on a metal part of the rear light assmbly it should work there and if it doesn't it'll be a duff light unit . In the past I've known people connect extra earth straps between light unit assmbly and mudguard and also between mudguard to frame . A guy who showed me how to first rewire an A10 years ago hammered home the message about earth fittings being clean ,bright and tight. Then even 6v lights shine bright and ok (just about ) ,best of luck BobH
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Well, it seems bsa-bill got it right first go, although how he knew that I had three bulbs with faulty/blown brake filaments is beyond me! Well done Bill.
I checked all the wiring, dismantled the switch, cleaned all connections and earth, but got nothing despite trying three different bulbs. Then in desperation I tried a 12v equivalent from my car bulb kit and bingo! It worked. Not bright enough, but at least I knew it worked. Off down the shops for two 6v 21/5w and both work.
Thanks all for your advice.
Paul