Start with getting a schematic for the car and finding out how the system works. Once you know how it should you are in a better place to figure out why it doesn't.
It could be something as simple as a relay, a terminal working its way out of a connector, or a brush in the motor. Or another issue.
Whatever that mechanic did may have made it worse, even though I'm sure he meant well. Come back and let us know what you've found out and if you need more help.
It could be something as simple as a relay, a terminal working its way out of a connector, or a brush in the motor. Or another issue.
Whatever that mechanic did may have made it worse, even though I'm sure he meant well. Come back and let us know what you've found out and if you need more help.