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. 

When I use the heated windscreens, I get a rattle / buzzing noise from the alternator because rac tested it and it was displaying 38.6v when using the windscreen heaters. Not sure if its related. 

Any ideas how to rectify the issues please? 
 

Thank you for reading, Ill appreciate all help. 

 

 

 

 

 

38.6v ?

only about three times what it should be 

Your electrics would be somewhat stressed at that voltage, but it seems like it will be an electrical problem some where.

Have you done a self test, as outlined in the Haynes manual ?

Sorry about the delay in replying, didn't get a notification about your reply. 

Haven't got one although I've searched lots of times without any success.