Engine Running Sense Wire???

[0-TJ-0]

I haven't really ever thought of using them but a couple things I've ordered recently came with them pre-installed. I don't use them because I have some easy access ign/acc points already setup. Perfect for simple little things like you want though.

[pollenface]

I soldered a wire to the back of a cigarette lighter socket to use as a sense wire for relays and things.

Alternatively you could go with a voltage sensing relay which only connects when the alternator is making upwards of 13.3v