Hello all,
I just bought a retired 2003 Dyna Defender (FXDP) and I'm having a nightmare getting the brake light to work. I checked the pressure switch on the rear brake and the relay. I checked for voltage at the bulb socket as well as the four pin connector where it plugs in. I've changed the bulb. I swapped the pigtail socket wiring for the bulb with a working one from a Sportster. Both pigtails work on the Sportster, neither works on the FXDP. I know they cut a bunch of wires when they removed the police lights, siren, etc. My only thought is that there's some extra ground loop or something goofy going on with the ground.

The running light comes on fine but the second bulb element will not light up when the brakes are applied. I verified that I'm getting 12v (constant as well as when the brake is applied) on the correct pins at the light socket as well as on the four pin plug in the light housing. I checked the continuity of that ground. Hell, I even checked the voltage and continuity vs. the sportster tail light. It all matches as far as I can tell but the dang thing still doesn't work.

Any thoughts? Thanks!

 

Here is the full wiring diagrams for a 2003 FXDP, hope it helps.

https://app.box.com/s/udfahjj7fie36ulakj0c

 

Thanks a bunch! This will makes things a bit easier to trace!

 

Yea, check the wiring diagram. I have an '04 Defender & the brake light didn't work when i got it. It was simply a blown fuse. The brake light is on a different circuit than the rest of the lights. Accessory circuit where a lot of the police emer lights were routed. That might not be your problem, but was for me.

 

I checked the fuses first and I didn't see a blown one. There were a little corroded though. What's driving me crazy is that I see good voltage to the brake light pin when the brakes are pressed. So voltage IS getting there but it's not lighting the second bulb element. That's why I think it's something ground related. I'm going to trace back from there via that diagram and see if I can find a faulty ground or something.

Other than that I'm loving this bike. The previous owner had the 103ci stroker kit installed and it has all kinds of power.

Thanks for the replies.

 

Nice looking bike without out all the Police stuff. Hate electrical problems but you seem to know what your doing. Good luck.