Dear mid-60s Buick electricians,
Rob Siegel is continuing to offer electrical troubleshooting advice on the Hagerty blog. If a component isn't working, Rob suggests that you wire the device (our hypothetical electric motor) to the battery and see if it spins. It’s that simple. Here is Rob's posting with the full explanation:
https://www.hagerty.com/articles-videos/Articles/2017/08/02/troubleshooting-electrical-problemsHe suggests that you create specialized test leads with a fuse so that if you accidentally drop your leads they won't create a short circuit. The fused test leads is a good idea, but I think there is an even better one. Try to get your hands on a hobby DC power supply such as those used for model railroads or slot cars. With one of those you can bring up the voltage gently and cut it off immediately if something goes wrong. This won't work for anything that requires a lot of amperage, but most things that you would be troubleshooting aren't using a lot of current.
As Rob points out, this test allows you to resolve whether or not the component itself has failed. Either way, that will save you a lot of time.
Cheers, Edouard
