underneath courtesy light

[Pike1915]

My underneath courtesy light isn't working and I don't know why.  I changed out the bulb still nothing. The cigarette lighter is getting power so I don't know why I can't get the light to work. Both using orange and white wires.  Any thoughts ?

[hatzie]

Dome works?
Year?

[Greybeard]

Push button door switch is rusted most likely. Easy fix.

[Pike1915]

My truck is missing both Door Jamb Switch's.  I tried looking through the holes to see if there was any wires but I couldn't see anything..  Anyone have pictures or a diagram ?

[Greybeard]

Depending on the year of the truck the switches could be simple one wire ground contact switches or two wire single throw switches. On one -open the door, the switch extends and grounds to the body of the cab and electricity flows through the bulb, it's that easy. The wire through the light/s is always hot (up to the switch). On the other there are two wires like a normal switch, one to hot and one to load. It is a simple inline switch. However you want to wire it. However, I think you would be hard pressed finding the one wire switch anymore. They didn't work all that great anyway. Bring one wire from a constant hot in the fuse panel to the drivers switch, run it all the way over to the passenger switch and terminate it there on that switch, this gives you two hot switches. Then run a wire from the drivers switch to each courtesy light and terminate it at the passengers switch. Ground each courtesy light to the cab metal. OR if you just want light for each door run two separate circuits; the hot wire can be the same way, but only run the drivers door switch to the lights on the drivers side and the passenger door switch to the passenger lights. But this way gets annoying if you want to set your favorite barley pop six pack down on the passenger floor when you get in on the drivers side and there is no light on the passenger side floor. 

[blazer74]

Should come on with the dome light. Does the dome light work with the headlight switch turned past full bright?
Same circuit, follow the wires back from the under dash light, probably cut or disconnected.

[Pike1915]

It is a 1974 k10.  There is no dome light I'm guessing they ripped that out when they ripped the door switches out. Both doors had plastic plugs where the door switches would be.  The  cigarette gets power.  the courtesy light has wires but no power.  So I guess it's really time to see if there is any other wires or if I have have to rewire it all...  If I rewire can I use any open auxiliary space in the fuse box?

[bd]

On the 1974 trucks the courtesy lamp acquires its power from the same fuse and circuit that powers the brake lamps and running lamps.  If the brake and running lamps function and there is no power to the courtesy lamp, the courtesy lamp orange wire has been unplugged or severed under the dash between the lamp and its splice with the other circuits.

Plastic plugs in the doorjamb switch holes usually means the door switches were never installed from the factory and the courtesy lamp, if original, is controlled solely by the headlamp switch.  It is always possible that the courtesy lamp is not original, but was installed later and never hooked up.

[Greybeard]

My 75 never had lamps until I installed them. The wiring is easy, like BD said, you can use the designated place from the wiring diagram (preferred) or choose any constant hot if you want the lights to come on when the doors are opened. If you want the lights to come on with the light switch too, things are a little more involved. Not hard by any means. I am lazy though so I installed the mentioned toggle switch to the left of the column that could be reached when the door was opened or closed. I am no electrician but that circuit is relatively easy no matter how it's done. Hot wire to whatever switches are desired, wire from switches to bulbs, wire from bulbs to ground. 

I just consulted my original (and very fragile) 1975 wiring book and it shows one courtesy lamp located near the left middle of the truck dash. The door switches were optional and were single wire grounding switches (I didn't think I was remembering that wrong), the hot wire (18 OR-40B; meaning 18AWG, orange, circuit 40 'B' meaning after a splice or load at/from the wires origin -the fuse-) comes from the behind the fuse panel on the end closest to the hazard flasher. This 18 OR-40B wire terminates somehow in a splice called splice 40 (also an orange wire), one wire from this splice goes to the light switch terminus 40C and the other goes to straight to the courtesy lamp (40D). That is one half of the circuit, the control half is a little more complicated since it has a few options that could, or could not, be present. Options like a cargo lamp, door switches, or a dome lamp. Those are all options BTW, not necessarily a given. The wire leaving the courtesy lamp is a white wire (18W-156) and it goes directly to the light switch terminus 156 (go figure). Inside the switch this is a simple grounding switch. If that is all that is required that is all there is. BUT, if there is a dome lamp, a cargo lamp, or door switches required/wanted then it goes like this...physically I don't remember what it looks like but the wires are thus

At the courtesy lamp terminal there will be three white wires at or near it, one is previously mentioned and the other two of these (18W-156B and 18W-156C) go to the door switches. Now if a dome lamp is wanted a wire (18W-156D) is spliced into one of these wires and run to the dome lamp. The other side of the dome lamp has a wire (18OR-140) which goes back to the back side of the Bat Fused terminal on the fuse box. These two terminals are fused through the accessory fuse next to them (20A). What this does is backfeed through the courtesy lamp back to the light switch which will control these lamps in addition to the door switches. Clear as iced tea?