First symptom: The shut-off switch does not turn off the car. It just continues to run. This is a switch that's worked perfectly in the past, with no changes I can think of. It's one of the 6 pole switches. One set of contacts for the main battery cable. A second set of contacts for the main IGN wire from the key. The third set of contacts grounds the alternator through a resister when the switch is turned off. I should also note that the engine was replaced this winter, but none of the wiring was changed.
Things I've discovered in my testing so far.
1. Switch definitely functions correctly. Verified all the contacts.
2. Car starts and turns off normally using the key.
3. If you try and shut off the car it does not turn off if you turn the key switch to off. Everything stays on. The alternator grounds correctly because the resister starts getting really hot.
4. Pulled the ignition wires off the back of the switch. Turned the key to ignition with the cut-off switch on. The IGN wire gets positive from the 12v constant wire on the key, goes to the cut-off switch, and then continues on into the harness. With the IGN wires disconnected from the cut-off switch and the key on, the IGN wire has power on both sides, which means it's getting 12volts from somewhere it's not supposed to.
5. If you go in the engine compartment and turn the key to IGN, even with the IGN wires disconnected from the switch, several things in the engine compartment have power.
6. Notably, the idle air control valve is making a high continuous wining noise. Pulling the IGN fuse makes the noise stop immediately
I haven't done any further investigation, but I'm planning to look at some wiring diagrams tonight.
Any thoughts on where to start?
thanks
Duncan