99 mustang radio and dome light does not shut off?

Just take the battery cable off everytime you shut off the vehicle


j/k I'd suspect the engine accessories switch is constantly activated. I'd look in the dashboard and see if you can find a short somewhere.

EDIT: I'd also like to know more about the car... does it have an auto start, did you install any audio equipment, has it been broken into and did someone attempt to steal the car, did you drive through a huge puddle lately, has the car been in an accident etc.... answers to these questions may help narrow down the problem.

Dude that sucks bad... there's nothing worse than trying to chase down electrical gremlins.

I'd start by removing the cover around the steering wheel and the panel down by the drivers side foot well. Get yourself a meter and measure each of the wires going to the ignition switch. There should be one constant power wire going to the ignition harness. I don't know what color that wire is, but I'm sure someone will chime in soon enough. If you identify other wires that are also hot with the key removed you may be able to isolate where the issue is and back track along that particular wire.

When you say you replaced the switch, which switch are you referring to?

I don't know what to tell you, other than to open up the column and get access below the dashboard and start poking around with a meter until you find the right wire.

I certainly won't claim to know everything and there may be an easier way to go about this, but whenever I've had electrical problems I find that its best and easiest to use a meter so you can isolate which wires are powered. This way you can locate a common location if it's several wires, or perhaps find a pattern that will lead to a resolution. If you choose to identify the draw using a meter, make sure the keys are not in the ignition, the door is shut, headlights are off, etc so you're only locating wires that are powered that shouldn't be. You know?