Electrical issues

Dear members,

I have a fiat coupe 20v turbo from 1998 since last friday.
However the coupe shouldn't have a lot of electrical issues there are a few.

When I turn the ignition on or start the motor my rear wiper starts going and only stops of I put the wiper stalk in interval which also doesn't work.
The AC and heater suddenly stopped working.
Also the voltmeter in the upright corner on the dash isn't working either. I'm sure there will be more problems as I go along getting the car up to shape but that's it for now.
A new wiper interval timer relay, E9 on the fuse panel under the dash, is on its way. hopefully that might fix the wiper issue.

Also also, what causes the higher pitch sound coming from the engine compartment ?

How can I track down what might be causing these issues ?

Very Kind Regards and Greetings from Belgium,
Cedric

Causes of electrical issues are, most often, difficult to identify, especially when there are several.

I guess a deep look at the electrical drawings will be necessary. You will find on the forum links for the workshop manual with these drawings.

Bad earth can typically cause all the issues you describe on any vehicle. If it was me, I would track down all the earth points and check them first.

Ok thanks guys I'll do some more research and take a look at the workshop as suggested.
Have a nice day y'all