So the other day I go to start my car. Turn key to on position without cranking and engine starts to crank and does not stop. I turn my ac off and it starts normal. I'm beyond confused by this. Anybody had any similar experience. Any help is always appreciated

 

Please tell us more about it.

Last maintenance, any mods, year, 300 or 400, any electrical issues elsewhere in the car?

 

Stock sc400 never had any electrical issues before. If hvac control head is on at all the starter stays engaged constantly trying to start the car. Turn it off and car starts fine. Flip it on with engine running and starter kicks in again.

It's a 93 and has had all maintenance done as long as I've had it, which has only been 8 months

 

You may have a short where the wires are touching and when your hvac is on it is trying to start your car.

 

I know the wiring in the sc300 behind the stereo doesn't seem to be insulated all that great. When i installed the aftermarket radio in mine, I had issues where i could here through the speakers when they rubbed together.