MTFCA Forum

My car is 12volt. 26/27. Equipped with SureFire ignition and older Texas T Alternator with inline diode . Headlights,taillights,brake lights all work. When I start the car engine runs for 5 seconds then fuse blows at start switch. All my wires are soldered and in good condition having replaced 7 years ago. Trying to figure out further searches. I pulled ignition switch yesterday and all wires were good. Noticed that inline diode wire is a little wonky but I don’t think that if even broken that it would shut down the engine. Any search ideas ??

Is the fuse in the main feed from the battery side of the start switch to the ignition switch? With the ignition and all accessories OFF, does a volt meter show a reading across the fuse terminals with the fuse out?

With the key and lights off, Use a Digital Multi meter set to ohms. Connect one probe to the fuse holder (fuse out the side going to the terminal block) the other to ground. You probably a reading of zero ohms or very few ohms Next disconnect one circuit at a time from the terminal board. When you get infinity on the ohm meter you have found the circuit that is shorted to ground. Visually inspect that circuit to find the bad spot where insulation is missing.

One place to eyeball is the hole in the firewall where the wiring passes through.

Easy way to find a short that has worked for me for 45 years is to disconnect one battery cable, it doesn't matter which one, connect a test light between the cable and the battery terminal. Replace any bad fuses. If the light comes on, there is a draw on the battery, so you disconnect one circuit at a time until the light goes out. That identifies the place to look in the wiring. On a T, I would start with the generator feed wire if it has one.