After suffering the dreaded instrument light rheostat melt down of the headlight switch on my 1974 911 Targa and successfully repairing all the wiring and replacing the god-awful-expensive switch, and fusing the instrument circuit off switch post #58a, the fuse blew immediately when I restored power. Thankfully it did its job and confirmed that a short in the instrument light circuit is probably what fried the headlight switch. I had recently had the speedometer overhauled by a shop that specializes in that and shortly after the speedo was reinstalled I experienced smoke coming from behind the dash the first time I turned on the headlights. I immediately went back to the shop that had pulled and reinstalled the speedo and the mechanic checked all the connections. We ran the lights and no smoke was evident. Months later driving at night is when the switch had a nuclear meltdown.
So my question is, when Ii originally researched this forum for information on how to replace the headlight switch I remember reading someone's post that mentioned they experienced an instrument light short after a shop had rebuilt their speedo, but unfortunately didn't bookmark the post and now I can't seem to locate it. In any case I am most interested in how I can troubleshoot to locate the short? My first thought is to pop the speedo and remove ll the light fixtures, then test each one individually. But is it possible the short is occurring within the speedo itself?
