Find the Source of Problem for Wiring/Electrical in Car has always been a very very Tedious Process. Apart from the long hours, we have to find out exactly, which is the wire that is giving the problem. And of course, a mismatch in soldering the wires back can give you more problems.
Only a Very Skillful Mechanic with many years of experience in diagnosing the Electrical System in the car would be able to solve the issue. Common Practise would be asking Customers to replace the Entire part to save on the time. But What if the parts aren’t that commonly available. Do you have another alternative?