Triumph Repair: engine not shuting off, electrical diagram, engine ignition

Question
Hi Jim, 1972 spitfire IV this just happened today never had troubles like this in the past. I haven't touched any wires or made any changes. If I turn the key off with my headlight on the car stays running, and will turn off when I turn off my headlights. If the headlights are not on everything works fine.. weird.... any thoughts of what could be going bad? Thanks Mark

Answer
Mark,

This is an odd one.  As delivered from the factory there was no connection between the ignition circuit (run from the ignition key switch) and the headlight wiring... apart from all drawing from the same battery of course.

I'm guessing that when the headlight switch is "on" then the headlights themselves are working correctly?

As a quick check, check the voltage at the + side of the coil with everything turned off.  Turn on the headlights (engine/ignition OFF) and see if you're now getting something on the + terminal at the coil.  If so, someone has done a bit of re-wiring, or at least misconnected something.

If that's the case, it's time to get out the electrical diagram and start tracing wires in the dash.  A common "bodge" involves wiring in a new stereo... I've seen some real rats nests of junk wire added in.

Cheers,

Jim