I have a si fiesta with a 2.0l mondeo engine in it. every now and then my front fog button lights up. when this happens i cant have any lights on with out the engine cutting out on me.(this includes the brake lights so it cuts out during braking and indicating all lights!) also when this happens my fuel gauge doesnt work I think this could be an earth but would like someone to tell me were to look for the problem. open to suggestions and really need the help thanks?

id get it looked at although someone on here may be able to help you
good luck

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Fiesta Si 2.0
Fiesta 1.1
Peugeot 206 sw 1.4

also sounds like an earthing issue to me, have you checked the earth wire on the drivers side of the engine? on the lifting eye?

there's an earth wire on the gearbox and make sure all the wires are connected to the - side of the bettery, also might be worth cleaning the surface areas on these places

other than that not sure what else to suggest, was it ok before the engine went in?

All my 4 aux buttons light up randomly lol... but it hasn't made my engine cut out :s
Does sound like some sort of earth fault though

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She's still alive! -23/02/2017