I have a strange problem with my '87 F-350 CC. A year or two ago, only during cold weather at night my interior and cargo light would come on all by themselves. You could go out and turn them off by turning them on an off a couple of times at the headlight switch. Look out the window an hour or two later and they're on again! Bad headlight switch, right ?, wrong... I replaced it and it still does the same thing. When spring came and it didn't get as cold at night they wouldn't come on but during cold weather I was greeted by a well lit truck every morning when I went to leave for work. But in warm weather they would stay off.
About May I bought a new stereo for the truck and an installation kit plus a wiring kit so I could use the origional plugs. Read directions carefully, went inside under good light to make the wiring connections from the radio to the wiring kit, double checked my work, all is OK and as instructed. Installed the radio and it works like a dream, but, when I shut the door the interior light and the cargo light stay on. OK, no problem, pull the #4 fuse for the interior light... The radio no longer works, which is odd because there is a different fuse for the radio. So here is my delima, I can either go around with int/cargo lights on and have tunes, or pull the fuse and kill the lights and ride around in silence.
I have looked, I have traced, I have replaced fuses, I have prayed cussed, and scratched my head and still havent found an answer... I am baffled... Please help... I you all can't help me I fear my only option left will be an exorcism... Maybe Elvis left the building and got in my truck...lol.

 

The radio uses the same fuse and circuit as the courtesy lights(the lightgreen/yellow). The radio has two power feeds to it. So no mystery there, you still have the same original problem with the courtesy lights that you had before.

For the original courtesy light problem, the first thing I would do is get behind the kick panels of all the doors, and disconnect (and tape off if you need to) the wires to each door switch. If the problem goes away, then you must have a problem with one of the door switches. Maybe one of them is barely being made, and when it gets cold, the sheetmetal of the truck is tweaking enough to turn them on? Of course if it still does it with all the switches disconnected, you can eliminate them as the cause.

 

Thanks for the reply.

I thought switch too. I tried taking a known good switch from another truck and trying it in the drivers side but no change. Tried that switch on the pass. side and still no change so I put my originals back in. I know the interior light fuse is #4 and I believe the radio fuse is #7.
I do recall that when I replaced the headlight switch a couple of years back I noticed the plug had a burnt place on it so I replaced it. In the process of rewiring the new plug a wire touched the headlight switch and the radio came on. I thought that was odd, but didn't think much of it at the time since all the wire colors matched up. Could it be that someone has switched the radio illumination wire with the power wire for the radio ? Not sure which wire that would be. That's the only way I can think of that the radio would come on through the headlight switch... I did try switching the power and illumination wires on the adapter kit since the directions said to use either one. The stereo is digital and would need an always hot to keep the clock from clearing every time you turn off the truck. Is the wire you mentioned a constant hot for the Int. light ? You used to be able to make the lights go off closing the door and turning them on and off a few times with the headlight switch, but that doesn't work anymore. I had replaced the headlight switch a couple of years ago, but that didn't cure it either.

 

The same wire that feeds the courtesy lights feeds the always hot on the radio. The illumination wire is blue/red. The always hot lightgreen/yellow radio wire is at the headlight switch for the manual on domelight function located in the headlight switch ****(when you twist it).

I see you messed with the front two doors. Didn't you say you have a crew cab? Does it have switches on the rear doors?

 

No switches on the rear doors. I'll check and trace those wires. It appears someone has either switched or crossed them somewhere. As far as I know this truck has no courtesy (under dash at the kick panels) lights, but since I've never seen them come on it's possible they weren't working when I got the truck. I'll have to look to make certain they're not there.

 

I said "courtesy lights" in my post, but just for your info the courtesy and the domelight are all tied together, so they are one in the same as far as the circuit is concerned. They are all fed by a black/lightblue wire. The lightgreen/yellow feeds the switches, and the black/lightblue leaves the switches and feeds the lights.