Rear wiring loom / odd brakelight behaviour

[jj]

On-course to get the car back on the road tomorrow (maybe tonight) but stumped by a weird problem with the rear lights.

I hooked up the wiring loom (multi-plug thing plugged in) -
Indicators, OK, sidelights, OK. Went to brake- numberplate lights came on as well as 3rd brake light. No outside brake lights.

I then spent about an hour fiddling with everything i could find which resulted in this -

Indicators, OK sidelights, OK, with sidelights OFF- all 3 brake lights work OK - with sidelights ON - when i brake, the NSR brakelight goes off, and the OSR gets mega bright. When sidelights are on, the OSR sidelight is brighter.

Totally stumped and pulling hair out so any help appreciated. At this point the front headlights dont have bulbs in nor are the front side repeaters, just in case this could make any difference. The battery also has been on charge for the last few days as it was flat.

[roadboy]

It sounds like a bad earth matey. Have you traced the earth wires back through the loom?

That would be my guess.

Dan

[robin]

What he said. Disco lights are always caused by bad earths ...

Cheers,
Robin

[jj]

I am guessing the earth at the battery end would make a difference - as I dont think I tightened it up since it was off disconnected - will check it when I get home. Thanks chaps

[robin]

More likely to be a missing earth closer to the problem. The most likely candidate is the rear harness connector which is bolted to the ECU panel in the boot on earlier S1s - not sure where it sits on later ones - anyway, it's the one nearest the immobiliser unit. Check inside that for corrosion.

Failing that, the ECU earth stud should be investigated as this is the ultimate source of the earth.

Cheers,
Robin

[philthy]

Turned out to be a corroded terminal on the brake light fitting.