Ford escort van 1.8 diesel.
When side lights are on, if brake applied both rear near side brake & side lights go out. If side lights on all ok problem only occurs when brake light comes on. Both brake lights work correctly if side lights not on.
I think this is acommon problem with Fords but cannot find any info - haynes manual absolutley useless
On the offending light, take out the bulb holder and clean with wire woll. Mine did it on the mot and 5 minutes work cleaning all the contacts cured it.
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