Dome Light Wiring

[turbojimmy]

Hi all - I have what I hope is a really simple question, but before I get to it I need to explain what I'm up to. I have a '94 Cadillac Fleetwood stretch limo. I'm in the process of re-doing the lighting. The dome light in it looks like it's out of an early 70s pickup truck. It's something the coach builder installed and I want to get rid of it. After an extensive search, I found that the best looking dome light that is a suitable size and style is from a Mustang. I bought it off of eBay, it was listed as a dome lamp for a '94-'04 Mustang. The existing light has a center bulb that comes on with the doors and 2 map lights on either side. The Mustang dome lamp is the same: center bulb and lights with switches on either side. The existing light grounds through the mounting screws to the body and has a constant hot feed. The map lights use the body ground to illuminate. The light that operates with the doors gets its ground from the door switches. So, there are 2 wires: one hot, one switched to ground for the doors. The Mustang light has a 3-position connector on it. Wires are green/yellow, black and black/light blue. If I hook the green wire up to hot, and the black/blue to ground the lights only come on with the map light switches. Both the center light and the map light come on. If I switch the ground to the black wire, just the map lights work with the switches. So, my question has to do with how the dome light in your '94-'04 light functions. Does the dome light always come on with the doors, or can you disable it somehow via the dash? Do all 3 bulbs light with the doors, or just the middle one? Does anyone have a wiring schematic to tell me which wires are connected to what? I assume it's the same combination as my Caddy: constant hot, ground and switched ground. Thanks for any help you can offer!

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[turbojimmy]

I figured it out. I found a thread on the Ford Ranger forum where a guy was putting a Mustang dome lamp into his truck.

The problem is that unlike the GM cars, the Ford lights are switched positive. That is, rather than the door switch completing a ground, there is a module that sends 12V+ to activate the dome lamp when the door opens.

So, like nearly every other project I embark upon, this one wasn't as simple as I had hoped.

I had to make a wiring harness using the stock Ford dome lamp plug and a relay:



Luckily there's plenty of room up in the ceiling to tuck in the relay and wiring.


Here's the old lamp. It wasn't very bright because the lens had yellowed over the years. Plus I didn't like the chrome:



Here's the Mustang dome light installed:



It looks much more modern and is brighter. I plan to put LEDs in it, but this is good for now.