Thread: Problem with TD5 Defender trailer lamps & fog lights

I have a problem with trailer lights & indicators when connected to my TD5 Defender.

Indicators work fine on trailer, until brake is applied. Then the fog lamp indicator comes on on the dash (dimly), as does the rear fog light on the truck (dimly) and on the trailer the indicator is flashing but everything else is too (dimly). When I switch the lights on the truck and apply the brakes with an indicator, then all indicators/brake lights are flashing brightly on the trailer (not synchronously!)

The trailer wiring on the truck is spliced into the rear bundle - left/right/tail/brake/earth. I have a brake controller, but I disconnected that to exclude it. I also pulled the fog lamp fuse and still get the same issue.

I can't quite work out how the brake (to a lesser extent) and lights (to a greater extent) are feeding the fog lamps & indicators. I know there is a diode on the fog lamp circuit at the rear - but nothing is tapped into the fog light wire. Seems to me that the lights on the trailer are drawing high current which is being fed back somewhere? Like I'd know! When trailer is disconnected, the truck is fine. Interestingly, when all this is going on, the trailer indicator in the dash doesn't light up (except for the obligatory one flash)

Driving along the indicators are fine, so doable during daylight hours as the other lamps are only faintly flashing when I brake, but at night when indicators/brakes/lights are on it is a regular disco behind me (no pun).

Does anyone have any clues?

Originally Posted by Gaudough

Definately a poor earth somewhere.

Regards Gordo

I haven't found it yet, but I jury-rigged an earth from the battery to the socket which fixed the problem - so it's in the deefer end between the bundle and socket ...