Get a schematic. If you dont know how to follow it, post it here.
Throwing parts at electrical issue is the worst option. As you already see it gets expensive quick.
Imagine:
If the 2nd new part you put in was defective. The third part was the actual bad part. How will you ever know? If the wire harness has a bad connection, all the components are good and replacing them all wont fix it. It’s like your favorite number is 5 so you always pick horse number 5. You may win once in a while, but out of 12....?
some people use a lightbulb style test light, better is a multimeter. But best is a power probe 3,4, or the Hook. If you want all in one get the Hook. I prefer to test ohms with a multimeter, so I use the 3. There are videos that walk you through basic use and just playing with it will get 98% of people comfortable within a couple hours. Sounds like a pain, but being able to track electrical problems for the rest of hour life is well worth it. The only key rule is if the rig has airbags, learn that cars color wiring warnings for them and NEVER mess with airbags. The invention of the powerprobe turned thousands of guys that could only change batteries and starters onto chasing down and finding electrical problems instead of R&R parts guys.
