Strange electrical problem

[shchuka]

I'm back on the forum after a few months away - YAY!

And I have a problem to solve - and need your help.  Got my bike through MOT yesterday (I'm in the UK) - it came through ok, but the mechanic pointed out a strange thing to me.  If the lights are off, then brake lights are working fine; if I turn the lights on, then of the two rear lights only one comes on (the one on the right) and the tail light on the left goes out.  He suggested to look at the ground side of the wiring.  I'm planning to spend some time on it tomorrow (weekend is always a good time for such activities).

In the mean time, any suggestions on specifically what/where to look for?

Many thanks!

[twinrat]

turn your light to park then check light ,i left my parklight which is the left tail light on and flattened the battery in 8 hours accidently ..

[shchuka]

I don't think parking light got anything to do with this.  It's clearly a wiring issue, as the same light works when another circuit is open and doesn't work when another circuit is closed.

[sledge]

Dual filament bulbs?  .....3 things to check

Make sure they are fitted correctly. They have offset pins and should only go in the holder one way but its not impossible to force them in and get it wrong. Secondly check each bulb and ensure that nothing has blown internally and shorted the two filaments together. Finally ensure the contact surfaces are clean and corrosion free.