Side lights come on when brake pedal is pressed


Hello to all,

I'm new here and am really posting on behalf of my Father who has a FourTrack 2.8TDS, I've used the site for reference material in the past which has helped him out, I've searched for the site for my answer to this one though and am not having much luck.

The problem:

When you hit the brake pedal the side lights come on, the 2 in the front bumper, the 2 small lights in the head lamps and the lights over the rear number plate.

Coule this be an earth fault or is it more likely to be a shorted connection somewhere?

If it's an earth fault could someone please list where the eath connection points are (I can obviously see the ones under the bonnet) so that I can clean them. If not likely to be an earth fault can anyone suggest where I should start looking for connection problems?

Any help muach appreciated,


Short Circuit

Hi Kev,

You could have a bad earth to the rear lights but if the indicators do not react with the brake and tail lights when they are turned on then it is unlikely to be the earth. Also i think the wiring on these Fourtraks is 'earth return' which means the power is fed to the lamp all the time then back to the switch, the switch then provides the earth. I'm not an electrical expert so i can't be sure i've explained that clearly (or even correctly)

My first port of call though would be checking both stop/tail light bulbs. Firstly to check that the correct bulbs are fitted. They should be twin filament, double contact with offset pins, someone may have fitted an incorrect bulb causing a short across the bulb holder contacts.

If the bulbs are correct type then try removing the left hand bulb and test whether the fault has been corrected, then refit that and try with the right hand bulb removed. If the lights work properly with one bulb removed then that is the faulty bulb. Sometimes when a stop/tail bulb blows the blown filament from drops onto the other filament shorting the two circuits together.

i hope this is some help, Diesel-Daz

Totaly agree on the bulb issu

Totaly agree on the bulb issue. Just one point though, it's only the headlughts that are switched earth. The side light circuit is standard switched feed. Japaneis wiering. Go figure.

Any veiws expresed in this thread by me are purely from my own experience, and (sometimes) falible memory. Hope my comments help, but please don't take them as gospel.

Sorted it out this morning.

Sorted it out this morning.

It was a dual filament bulb and one of the filament arms had broken and was resting on the other, so hit the brake pedal and it power up the brake lights and this then transfered across to the side lights.

2 minute job - well it would have been if I didn't have to drill out the bolts holding the lense in place.

Cheers lads,


Main & Dipped beam interaction

Glad you got it sorted. It's also one to watch for if your main & dipped beams start to come on together