1976 Triumph Bonneville T140V brake light problem

[silverfox41]

I'm finishing up restoring my 1976 T140V and noticed I don't have any brake lights. I checked the rear brake light switch which has continuity and the 1157 taillight lamp is good. I have 12 volts with the White wire coming from the flasher.I have continuity between the rear brake switch and the lamp holder. The taillight works so I have a good ground. I opened the headlamp shell and noted one Brown/Green wire with a spade connector that is hanging free and not connected at the lighting switch. I have no clue as to where it is suppose to be connected or if its a spare. And I found a Yellow/Blue wire and a Brown/Green wire that appears to be cut off and taped up also inside the headlamp shell. Does anyone have a suggestions to help me to get my brake lights working. Thank you.

 

[hemibee]

I've got nothing for you on this one, hopefully GranPaul will be along shortly, he will probably have a good idea of what needs to be done.

 

[The Seeker]

I'm finishing up restoring my 1976 T140V and noticed I don't have any brake lights. I checked the rear brake light switch which has continuity and the 1157 taillight lamp is good. I have 12 volts with the White wire coming from the flasher.I have continuity between the rear brake switch and the lamp holder. The taillight works so I have a good ground. I opened the headlamp shell and noted one Brown/Green wire with a spade connector that is hanging free and not connected at the lighting switch. I have no clue as to where it is suppose to be connected or if its a spare. And I found a Yellow/Blue wire and a Brown/Green wire that appears to be cut off and taped up also inside the headlamp shell. Does anyone have a suggestions to help me to get my brake lights working. Thank you.

Brown-Green wire = Tail Lamp

There's no Yellow-Blue in the wiring diagrams at all, but there IS a Blue-Yellow that goes from the lighting switch inside headlamp to the Hi-Lo dipper switch.

The brake light wire is solid Brown. It only goes from the brake lamp to the rear brake switch and to the front brake switch.

The spare Brown-Green might be the one to the pilot lamp if it's not being used?

Try used a wire tie to hold the front brake lever on/in and then try testing for 12v at the brake lamp socket. The key has to be turned to the ON/RUN position. It may well be a bad front brake switch.

Both front and rear brake lamp switches are supplied by a White wire directly from the ignition and lighting switch.

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[silverfox41]

Thanks to all for your help. Upon further investigation I discovered that the brake light is illuminated all the time instead of the taillight. I disconnected the rear brake switch and the brake light still remains illuminated. I measured the voltage of the Brown/Green wire for the taillight under the rear fender and I don't get a reading. I will next try to locate the front brake light switch and see if this is causing the brake light to be on all the time when the ignition is switched on. As far as finding why I don't have voltage to the taillight is another problem. The former owner is deceased so I can't get any answers to what he did to the wiring.

 

[CarlS]

Tracing out electrical problems is often a painstaking, frustrating process. But when you solve the problem, you feel really good.

 

[The Seeker]

Remember that it's POSITIVE ground/earth.



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[silverfox41]

Thanks to all for your help. I discovered that there was a wire that was not connected to the headlamp switch and this fixed the tail light problem. And after numerous tests I disassembled the front brake switch and cleaned and readjusted it. I also cleaned the plug in connectors under the seat and now the brake lights work as they should. So my headache is solved and this 37 year old bike is now street legal again.

 

[CarlS]

Success! Nice work and thanks for the follow up report.

 

[The Seeker]

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[Rocky]

Great news