Electrical assistance please

[210bhp]

I was on a run out during daylight with the Scottish crew last weekend and Jon following said my offside brake light wasn’t working.

Investigations had to wait for today and this is what I’ve found. Perhaps the electrical gurus on here could point me to the problem. I first checked all the bulbs and fuses and all appear fine. Then I cleaned the earths at the rear lights and the one to the body (the nearest one on mine actually connects to the oil tank?)

Swb car
Engine running


1. Side lights on and all working front and rear
2. Press the brake pedal and the nearside rear brake light works but not only does the offside rear brake light not work but it puts off the side light
3. The side lights off and press the brake pedal and only the nearside brake light works.
4. If I disconnect the sidelight wire from the bulb holder on the nearside obviously the side light on that side does not work but the offside light does when the switch is on. Furthermore, if I now press the brake pedal both brake lights work.
5. If I leave the nearside side light wire disconnected and leave the side light switch off then both brake lights work fine as in 4.
6. If I disconnect the side light wire on the offside the side light nor the brake light works on that side but the side light and the brake light (whether the side light is on or off)both work on the nearside.

Any pointers welcome please

Regards
Mike

[PeterK]

Sounds like earth on the offside can’t handle the current.
Try a temporary extra earth to check.
Peter


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[Jonny Hart]

I think the clue is in your statement about the earth being on the oil tank. That doesn’t sound right.

[DustyM]

Oil tank mounts through rubber bushes so not much of an electrical circuit there!