As I've heard with Fords, the wiring tends to "go" on older trucks, particularly in the northeast. I've been correcting issues with rotty wires and corroded grounds since I've owned it, but here's one I can't quite pin down.

A couple weeks ago when I pulled the headlight ****, the front headlights came on, and thats it. No taillights, park lights, roof lights, or gauge panel lamps. I jiggled the **** back and forth, and eventually the other lights flicked a few times, and stay on steady. Unless the engine is running, none of the "exterior lamps" will ever come on, just the headlights. Pulling the **** to parklights does nothing with the engine off. For a couple weeks it's been flickering when I first turn them on, but stays on steady after that. All the fuses are fine.

My truck does leak in the rain. I assume it must be from one of the roof lamps, since it runs down the center of the windshield and drips off the mirror. I checked out the wiring under all 5 lamps and nothing looked rotted or damaged. I'll probably put silicone on them in the spring, too cold to apply now.

Just today, I got another weird problem. The engine suddenly ran extremely rough for about a minute(RPM gauge was jumpin all over the place), then just as quickly everything went back to normal. The chime noise for "headlights on/door open" is now on whenever the lights are on, but only if all the other lights are on (if I turn the lights on w/engine off and ONLY the headlights come on, it doesn't ding). I figured the door switch was bad, but that's fine. It turns the dome/door light on and off normally, but won't shut the dinger off. I know I can just unplug the dinger thing, but I suspect this is an indicator of a larger issue.

Where should I start testing for a short? Are there any big "hotspots" for electrical shorts?

 

The chime thing has me thinking a bad ground connection is causing your light issues. That's usually what you've got when things come on randomly like that. It seems like there's a chime circuit that only activated in run and the lights found a ground(short to ground) through that circuit.

 

I pulled the door switch button out, and there was a small bare spot where it rubbed on the metal. Taped over that, and now the dinger stopped and the dome light works again, but it still has the odd light issue.

I cleaned the ground terminal on the battery and the big one right next to it. The battery clamp on (-) was pretty bad, cleaned that up with baking soda and a wire brush. Voltage is slightly higher now when running, but it did nothing for the light issue.

It seems the cold has something to do with it too. When I start it on a cold morning and pull the lights, it takes a few seconds until the ext.lights start flickering, they flicker for a sec or two, then stay on steady. Once the truck is warm, they turn on and off normally with the headlights even if the engine isn't running.