Very dim rear light - Help!

Hey all,

Been having issues with the tail light on my '04 Bonnie and I'm needing a bit of guidance.

Tail light comes on when the ignition is turned either on or in park but it is very very dim, at some points seeming to fade till it is pretty much off. It comes on nice and bright when braking and the number plate light also brightens with braking (which I am not sure it should).

The tail light (and indicators) aren't stock, the previous owner fitted something like this: http://www.squaredeals-ltd.co.uk/tr...racket-miller-style-black-housing-33427-p.asp . Not sure how well it has been wired but has been fine for the last 6 plus months. There are a couple of resistor in line with the wiring under the rear fender (pretty exposed to spray from the tire) that give me a little concern, I assume at least one of these is wired to the tail light rather than indicators, don't know if it could be responsible. Bike has got pretty wet and horrible riding through the winter.

Only electrical change I have made recently is to fit a new horn, one of these: http://www.squaredeals-ltd.co.uk/lo...109db-upgrade-for-oem-triumph-horn-1817-p.asp . Not sure why this would effect anything since as far as I can tell the horn is separate from the position light/tail light circuit. All the other electronics/lights etc appear to work fine.

So far I have tried cleaning and tweaking the plug for the tail light under the seat and I have checked the relevant fuse (fuse 10 I think), all to no avail. Any suggestions on key things to check to try and fix this? Need any help I can get since I am currently taking public transport to work .

 

Will have a check for earth faults and whilst I am at it I will check every possible connection I can get my hands on. I would have thought that since the tail light only has one earth for both running light and brake light that an earthing issue would effect both but I am a total newbie to vehicle wiring.

 

Will dig out my multi meter or borrow one from work. Changing the bulb is a no go since it is an after market led light.

 

Finally had the time/weather/daylight to track this fault down. After checking and cleaning pretty much every electrical connection and fuse on the bike I found the ball of electrical tape that marked where the previous owner had spliced the aftermarket light onto the harness. The copper crimp connector inside for the running light had literally corroded away. It was like it had been smote in the tiniest act of God and turned to a pillar of green salt. Unsurprising since the splice was just before the wires pass through the fender to the light, putting these connection directly in the path of spray from the wheel. I'm going to tidy the wiring and redo each of the crimps with a well sealed solder joint, should be all good.

 

Cheers Mick, that's the plan. Big tube of silicone grease in the lab at work for sealing epoxy molds so I'll "borrow" some and apply liberally. Couldn't believe the last guy wired it in such an exposed place with nothing more to seal it than a length of badly wrapped tape.