Car Stereos: How to Find Power Source for Wiring?, inline fuse, using a multimeter

Question
Hello,
I have a 1970 Dodge and would like to install a new car stereo. It currently has a stock radio.  My question is how I would be able to find the proper source for switched power for my new stereo unit?  

Do you recommend splicing into an existing wire? Or is there something in the fuse box I should be looking for?  Just wondering what is the safest and easiest way to get power to a new stereo unit (or gauge ...that I plan to try after after I finish the stereo install project).

Thanks very much!

Answer
Hi Brad,

For the actual power, I'd suggest running a fresh power wire off of the battery with an inline fuse in the engine compartment, and another inline fuse somewhere behind the dash.  Fuse it a 15A.

For ground, I'd ground it out directly on the chassis on a clean, (preferably sanded/filed), unpainted, not-welded surface with a ground wire that is < 18" (the shorter the better) long.

For accessory, you'll need to find that with some searching. Using a multimeter, find a wire that's carrying 12V when the vehicle is in accessory (if there even is one in the vehicle -- there may not be), or on.

If you can't find one, you might want to just run the same 12V wire to the accessory lead on the stereo aswell, but just put a switch on the dash somewhere interrupting it so you can turn it off when you get out of the truck -- just beware forgetting to turn it off might drain your battery.

Good luck,
Justin