Alternator fuse
 

Dose anybody know if the alternator fuse in the fuse box by the battery is only to engergize the alternator coil, or is it a live circuit as long as the engine is running?


I am asking because I need to add a circuit to fire a relay, like this:

http://www1.cooperbussmann.com/image...7bb04a08b9.JPG

Just need a constant power source only when engine is runing.

It's definitely not to energize the coil. That's done by a PWM signal from the IPDM (which is how your car can run the voltage higher if the battery is dead to charge faster, etc). Usually the alternator fuse is there to make sure something doesn't dead short the alternator and burn it out. Honestly though if you're looking for an ignition on power source you need to use something behind an ignition relay. Usually the alternator and the in-line fuse for it are just run in series with the battery, so if your car shuts off you'll still have battery voltage...

Thanks..I found a circuit in the fuse box beside the battery. It houses the fuel pump fuse...and a lot of others. I can't remember which one I taped off of now, but it worked out great.

Sorry it's in parallel with the battery. Make sure to use an in-line fuse for whatever you're running, wouldn't want to have something go wrong with it and shut off your fuel pump. lol

For sure. I did not use the fuel pump circuit. It was a windshield washer circuit, so a very minor circuit in the grand scheme of things.