I failed my MOT today because the rear right lights were misbehaving. Where am I best to look for a problem, just the earth on the rear right or the earth to chassis join?

Start with the bulbs and bulb holders then move onto the earths. It's often internal failure in the twin filament stop/tail bulbs.

Didn't you check the lights before you went?

adrian

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Originally posted by adithorp
Didn't you check the lights before you went?

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Has it rained heavily near your neck of the woods? Could just be a soggy terminal.

I'd start waggling wires and trying and localise the problem that way.....

First off, is it your kit car or tin top. Which lights are misbehaving and are they all in one unit or single units???

As mentioned above, check the bulbs first, then have a good look at the terminals that the bulb pushes on to. I have known them corode.

Cracked wire in to the light unit, then have a good look at the earth points in particular where they mount on to the chassis/body.

Steve

I think its sorted now. It was the kit car. My garage is along a muddy track to the road and the light electrics are in the rear arch and they were covered in damp mud. The bullet connectors were rusted solid. So I cut out the earth connector and soldered in some wire. Everything seems OK. The next dry Saturday we get after tomorrow, I'm going to replace the lot. It should get through the retest tomorrow.

Bullet connectors always were and always will be shite. Invest in some decent sealed connectors, at least for under the arches.

Have you checked the lights with them all working together (side,brake and indicator)? Earth faults often don't show if you check one circuit at a time.

adrian