Tail light not working

[Destructobot]

Just picked up a '99 M900 a couple weeks ago.  The former owner installed an integrated tail light.  I wanted to take it out at night for the first time today, but realized the tail light was not working.  Rear turn signals work and the brake light works, but the regular running light isn't there.  Any ideas?

[Ddan]

Check the connections under the seat

[stopintime]

When I installed my first taillight, I found that Ducati connected some wires backwards. +/- doesn't matter on a normal light, but must be correct on a LED light. Maybe that's worth looking into while you're checking all connections....

[Destructobot]

I'll have to open it up and take a look.  I would expect that there's a common ground for the different circuits, so I'm not sure if the polarity could be reversed.

[stopintime]

I'll have to open it up and take a look.  I would expect that there's a common ground for the different circuits, so I'm not sure if the polarity could be reversed.

I can't remember what the factory had done wrong - even if it shouldn't be possible (common ground) something was reversed - then fixed by swapping wires. I know it doesn't sound logical, but that's how I remember it.

[V-Twin_Fan]

Here is what I would do first.
-Check the bulb (there should be either a dual element bulb or two separate bulbs in there. One for the brake and one for
the running light) make sure they are not burnt out.
-The ground for the license plate and the brake light/running light are the same.  If you say the brake light works the ground is probably good if dual element but if two separate, check the ground on the socket that the bulb sits in to grounding point on frame.
-Check all the wiring to include connections, fuse and socket that bulb sits in for bent tabs

The only other thing I can think of is there are two dual element bulbs in which the thinner or smaller element in the bulb is the running light and somewhere it is connected up wrong.  For example the blinkers are connected where the running light should be.  One question for you, are the blinkers and brake light just as bright as one another or is one dimmer than the other?

[Howley]

Here is what I would do first.
-Check the bulb (there should be either a dual element bulb or two separate bulbs in there. One for the brake and one for
the running light) make sure they are not burnt out.
-The ground for the license plate and the brake light/running light are the same.  If you say the brake light works the ground is probably good if dual element but if two separate, check the ground on the socket that the bulb sits in to grounding point on frame.
-Check all the wiring to include connections, fuse and socket that bulb sits in for bent tabs

The only other thing I can think of is there are two dual element bulbs in which the thinner or smaller element in the bulb is the running light and somewhere it is connected up wrong.  For example the blinkers are connected where the running light should be.  One question for you, are the blinkers and brake light just as bright as one another or is one dimmer than the other?

He has an LED integrated tail light, so I think none of that will work.

[V-Twin_Fan]

Well, if it is LED the only thing you could do is make sure that you have electrical power for the running light at the tail kit. If there is power there, you might have something bad internal to your integrated tail light.

[Destructobot]

Opened it up and found a busted solder connection.  Five minutes with the iron and it was AOK