I have got a 1.4 ford fusion 06 plate, UK model. Virtually every times it's wet outside, my engine light shows up and rev gauge is often inactive, ie stays on zero. 

 

Car drives virtually as usual although not always with power when I need it, still does 70 though. 

I've replaced crank shaft sensor with an original one, still the same issue. I had also used a copy one, that was poor as it kept stalling when changing gears when at a low speed. 

 

Any ideas how to rectify it please? Been told it maybe a bad earth of which I suppose is a possibility, because when I use the heated windscreens, I get a rattle / buzzing noise some where in the engine bay although can't locate it, plus don't know where to check for a bad earth or how to rectify it. All lights etc work. 

 

Thank you for reading, Ill appreciate all help. 

Edited November 18, 20196 yr by Dave_from_Birmingham
Add uk model.

Bump 

Not a technically advanced fix, but you could try connecting some heavy duty cable from negative battery terminal to engine and some more heavy duty cable from negative battery terminal to the chassis. If it’s a bad earth it might help. But if starter motor and lights fine I am not sure

Thank you. 

 

Since writing the above, I've found out each time I press the windscreen heater, the voltage on the alternator increases to 38.6v. And there is a fairly loud buzzing noise from the alternatir Not sure if it's related or not.