Brake light / Indicator fuse

Learned collective…

Apologies for the long post.

Edited to update x2:

My FF had developed a fault whereby use of the brake light or indicators (either side) blows the fuse after a few seconds. Two or three flashes of the indicators was all you got before the fuse blew, and about three seconds of brake light operation before it too blew the fuse.

It turns out that there was a 10a fuse where there should be a 15a. This is the first time fuses have blown, so I replaced like for like when it blew on today’s ride.

Having replaced the 15a fuse, the right hand indicators work and don’t blow the fuse. The brake lights also work normally.

However, the lh indicators now don’t work. The bulbs are good. The flasher relay ticks as though it’s working, but nothing at the indicators, and the dash flasher repeater is VERY dim. When the flasher unit is ticking, the oil pressure and neutral lights dim in sympathy.

Update: I took the fairing off and disconnected - reconnected the plug with the orange wire in it (that goes from the switch to the indicators). That appears to have cured it. Insulation checked again and all is well.

As previously established, I am to motorbike electrics what Liberace was to Rugby Union, so any comments re why the 10a fuse was fine for ages, then suddenly wasn’t would be most welcome. I’m not convinced that I’ve actually fixed the fault that caused the fuse to blow, or permanently fixed the LH indicators.

Thanks, all.

Hey Chris,
You must have a shocking wiring harness, or electrical system on that bike. :slightly_smiling_face:
I was going to give you some ideas on how to check where the problem was but it seems you beat me to it. There must have been a loose or dirty connection in the plug and by removing and replacing the plug you have improved the connection. As far as fuses go, the 10 amp was ok previously if the connection was good and did not pull over the 10 amps but as soon as the connection started to fail it would have caused a high resistance in the circuit and drew more than 10 amps, so the fuse did the job and blew. I would suggest that you pull all the plugs one at a time and clean them all, blow them out with air if you have a compressor and spray with WD40 before putting them back together. If they are really dirty spray them with Brakeclean or similar. At least do all the connections in the tail section. Fault had to be at the tail or the front as they are the only two places that stop light and indicators are in a common area. Because the other small lights faded too I would clean all the earth connections to the frame as well because when an earth is not secure then the system tries to earth through another light or lights causing more amps through the circuit and again blowing a smaller fuse. Try it and see how you go. Again, any problems let me know.

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Thanks, John.

My knowledge of electrics is, shall we say, basic. I’m quite happy to use electricity but have no real understanding about how it works. I’m a mechanical engineer - if I can’t hit it I can’t understand it.

It would be so much easier if electrons were coated in dye so that any leaks would be easy to see.

I’ve disconnected, cleaned and reconnected all of the plugs behind the fairing and at the back end on the principle that if this circuit was compromised by dirty connections, the others in unrelated circuits won’t be far behind.

So far, everything’s doing what it says on the tin, as it were.


Keep going you will get there eventually.