Hello! I can't find a wiring diagram for a cargo lamp on a dent side. 76 F100 with a 300 6 and three on the tree. Truck is bare bones stock, no power anything. I got the lamp off a donor truck and would like to add it to my truck. Problem is, it has two wires coming off and the socket is for a dual-filament bulb. Also, the socket has the tab slots at the same level, as opposed to the normal hi-low tabs you see on a parking/brake bulb. I can easily splice the power line off the dome light and have it function the same, but the socket and wires have me confused. Anyone have a diagram or knowledge of how these can be wired up to a truck that didn't come with one originally? Any help would be appreciated!

 

Edit - After seeing pic clearly I am wrong -disregard below. apparently I confused this with another application
It wouldn't be a 2 filament bulb and that is confirmed because you said the bayonet pins aren't offset. The second wire is a ground. what color are the wires? Can you post a pic of the socket? Just have to make sure you hook them up properly so power wire goes to the center silver contact on bulb and ground goes to contact the outer bulb casing with bayonet pins.
Yes just splice it in with interior dome light.

 

Wires appear to be one solid black, and the other black/red. As you can see in the pic, the socket has a fitting for a dual filament bulb. Whole thing is weird...

 

So that looks to be the older style cab back/ cargo light with the metal body/glass lens right? You know you will need to tape in a switch.

 

Some dome light help I got from a fellow FTE member a while back. It is in 2 different parts. Maybe it will help?

For thedome light wire, hot-at-all-times power comes goes to the headlight switch as a GREEN with YELLOW stripe wire. Dome light power comes back out as a BLACK with BLUE stripe wire. The same color scheme is used at the door jamb switches. BLACK with BLUE stripe runs out to the actual dome light. BLUE with a RED stripe is instrument panel illumination. It comes out of the headlight switch to the fuse box, leaves the fuse box again as the same color and is distributed throughout the dash.

There is no ground connection to the dome light switches or the headlight switches. These switches switch power, not ground.

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1) Make sure you have 12 volts on both sides of the courtesy lamp fuse. This circuit is hot at all times, so it doesn't make a difference what position the key is in. If you have power on only one side, replace the fuse. If you don't have power on either side, then there is other work to do first.

2) Pull the dome light switches out and remove them. Make sure the terminal for the GREEN with YELLOW stripe wire in the connector has power.

3) Check the dome light switches for continuity. With the plunger all the way out (switch CLOSED), the switch should be shorted. With the plunger pushed all the way in (switch OPEN), the switch should be open. If not, replace the switch.

4) With power to the switch proven to be good, and the switches proven to be good, the dome light should light up. If the dome light does not light up, remove the cover and check for power at the dome light (not the side that's permanently grounded to sheet metal) with the door OPEN. If you have power here, yet the bulb does not lightup, replace the bulb.

This will prove out the door-side; if you get to the point that the doors turn the lighton but the headlight switch will not, then we can cross that bridge.

Yes for a 78 so maybe some wire color differences.

 

Here's the page from the factory wiring diagrams. The cargo light is in the upper right quadrant.
In the schematic the cargo light is called a utility lamp.

The cargo light has it's own wiring harness.
Using a factory harness makes the whole thing plug 'n play.
Wiring harness, courtesy light.
Fits: 73-77 F100-350 regular cab w/ cargo light
P/N D3TZ-13A709-C
I did a quick search and found one available.
https://nospartsltd.com/product/d3tz13a709c/

 

the 1973 cargo light takes a 1076 bulb...it has two contacts like a dual filament bulb.

 

Also, I did the same mod to my project ('73 F100) It originally didn't have a cargo light.
Here is the "plan" I made to cut out the hole in the roof.
One important note, the hole is NOT centered above the rear window. It's offset to one side. Us the centerline mark on the drawing as the center.

 

Here are some pictures of how mine turned out.

 

1076 bulb! This is the key. I knew one had to exist. Thanks!