Need help with dome light wiring and courtesy lights. I have a 79 F-150 and ever since I got it the dome light has not worked. Prior owner installed a new aftermarket EZ wire harness. Everything else seems to work great. I pulled the lens off of the dome light and bingo no bulb. Put in a new bulb but now the problem is the light doesn’t go off when the door is closed...

So I pulled the door jamb switch and the two wires coming off the door jamb switch are not wired to anything. Turns out previous owner who installed this harness has then wired directly to fuse block which explains why he pulled the bulb.

Im also adding LED lights under the dash that I want to have come on when the door opens. I’ve already got the LEDS mounted under the dash now I’m trying to figure out the best way to wire it all together.

My initial thought was power from the fuse block to the door jamb switch then tieing in the LED power wire to the “out” end of the jamb switch so they’d come on together but then I started thinking about passenger side jamb switch and how that’s going to tie in as well as the how to make them also come on with turning the headlight switch to the left....now it’s left me confused how to best wire it all....electrical isn’t my strong suit.

Any input is appreciated. Cheers.

 

Hey, no shame landers. Dome light wiring sucks!
Even when you think you understand it, you don't always. And you may be dealing with two different methods too. I have not looked at all the possibilities, but often GM and Ford used different switching schemes (such as switching the ground side vs the 12v positive side for example) and the EZ Wire harness is almost guaranteed to be using the GM method. Assuming it had dedicated dome light wiring in the first place. Which it probably did, but no guarantees with the less expensive stuff.

I'm guessing you figured out already that they don't use the original Ford colors, but instead use GM color codes. So books don't do you any good from the standpoint of colors. But at least EZ usually has nicely printed functions on each wire, so if there is a dome light wire, you'll know which one it is.
Supposedly the ones up at the housing are so marked?

Have you tested the headlight switch yet? Meaning have you made sure it's off of it's dome light position in the rheostat?
Most older trucks have kind of time dash lights, so the switch might get left on full bright without knowing it. With new harness though, usually they're much brighter, so that might not be your issue.
But it's totally worth a quick check in case EZ has it wired through the headlight switch, but the PO never got to the point of hooking up the door switches.

Probably because by that time their head hurt too!

Good luck.

Paul

 

I had a FTE member help me with my dome light issue in the past, here is his advice below. Yes your colors might be different with that aftermarket harness you have. Once you get the dome light working properly, with door plunger switches and headlight switch rotation, then tie in the underdash lights.

"For the dome 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.

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 sheetmetal) with the door OPEN. If you have power here, yet the bulb does not light up, replace the bulb.

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

 

And if you're using LEDs, beware that they only work with the correct polarity. If you connect positive to negative and negative to positive, they won't work.