Electrical issue
 

I have a 63 C10 and I have a wire coming out of the fuse block that I am not sure where it goes. It is coming out from behind the heater power wire. It is labeled B.U. LPS. I don't have clear back up lamps on the truck so not 100% that is what it is. This wire is brown and not very long only about 18" so it must have come out of something relatively close. Any ideas?

Re: Electrical issue
 

Both the heater & backup light options use the same fuse, 3rd one down from the top marked "HEATER / B.U. LPS." It sounds like you have the brown heater power wire plugged into the one of the terminals that's off to the right side of that fuse (which is the correct location). Is the mystery brown wire plugged into the other terminal right in behind the heater wire? If so, it might be something a previous owner plugged in there (and could be stock looking if they used an end cut from a spare heater power wire or something).

Or does it run farther in behind the fuse panel? If that's the case, it might be the wire for the fuel gauge. It was a brown wire for 1963 (changed to tan for 64 & later). That wire originally ran from the instrument panel connector down to a terminal on the fuse block marked "GAS GAGE". And from there, a wire plugged into that terminal ran to the sending unit.

Re: Electrical issue
 

It looks stock the way it is wired in. It is right behind the heater wire. Kind of a heavy gauge wire as well. Trying to figure out how to add a photo to this post so you can see it

Re: Electrical issue
 

Not sure if this is right but I think it has the pictures

Re: Electrical issue
 

I can't quite tell from the pic, but does that wire have the same type of black rectangular connector as the heater power wire? If not, it's definitely something someone added. But even if it does have the OE connector it could still be a section of wire someone salvaged out of another GM vehicle and used to power some accessory that has since been removed.

As you already know, that location would have been used to power backup lights if your truck had that option. There might have been some other options that sourced power from that location as well but I'm not aware of any.

Re: Electrical issue
 

You are correct, the connector is different. I am not sure what it powers/ powered. Guess I will just disconnect it till I find something that needs power! Thanks for your help I appreciate it.