Sounds like theres a short in the wiring thats grounding the switch in the colum, and burning it out. I had a similar incident working on my gauges in my car. (still trying to get them fixed). I wish I had more exp with wiring, I'd try to walk you through the troubleshooting.
What I can tell you is that the general method you should use would be to isolate each part of the system, and test them individually, looking for a break/drop in the power. The actual method of testing varies depending on the part.
Also, it would be a good idea to start by tracing the routing and just look for any physical damage to the wires.
Hopefully one of the more experienced folks here will be able to tell you more.
J
BTW Welcome to MW!
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'66 Mustang Coupe- AKA "Lenore" *on disability for a (long) bit*
'93 GT Mostly stock AKA "Fawkes"
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