hooking up a modern stereo in my 65 f100. I have the red power wire hooked into the fuse box with the connector next to the fuse where it is marked radio. This is key on, power on. Is there a constant on power source in the fuse box that I can hook the yellow wire up to?

 

Check the cigarette lighter if you have one, thats usually constant power.

 

and if I don't have a cig lighter?

 

door light?