Dome Light Help
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New User
Joined: Dec 2018
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From: Ogden, UT
Dome Light Help
I've got a '78 Ford F250. When I first got the truck the Dome light wasn't working. I ended up buying a new one and replacing it, but still no dice. I have no clue where to start with the trouble shooting, so any help would be appreciated. Thanks in advance!
Elder User
Joined: Apr 2016
Posts: 854
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Check the ground, especially if you have a cargo light. Clean the light posts with some 400 grit,they get crusty. Check for power at the light with a multi-meter. No power? Check your headlight switch. I forget which pinout for the interior lights is, but sometimes it's marked. No power there? Check for power at the fuse. No power? Run a jumper wire to the hot side of the light. If it lights up? Start looking for pinched or broken wires
Laughing Gas
Joined: Nov 2013
Posts: 1,207
Likes: 60
From: S.E. Louisiana;so far USA
If there is no power at the lamp, but is at the fuse, you'll just have to do as indicated; take your test light or meter and trace out the circuit. Then you'll be able to narrow it down and find the shortfall.
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New User
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From: Ogden, UT
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Moderator & parts slinger
Joined: Feb 2007
Posts: 50,188
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From: S/W Missouri, Polk county
A wise ol FTE member one said......
"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 yes is your head light switch (that rotates to turn on the dome light with the doors closed) working?
"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 yes is your head light switch (that rotates to turn on the dome light with the doors closed) working?
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Fleet Mechanic
Joined: Jul 2017
Posts: 1,448
Likes: 163
From: East Texas
One of the mounting screws serves to ground the assembly to the sheet metal. Check to make sure the mounting screw and hole are in good shape. We replaced ours and had to fiddle/clean them up a bit. I think we used a new screw.
Fleet Mechanic
Joined: Sep 2009
Posts: 1,572
Likes: 37
From: Northern Virginia.
fixed my dome light.
Thanks very much!
Fleet Mechanic
Joined: Feb 2005
Posts: 1,782
Likes: 15
From: Lower Mainland B.C.
A wise ol FTE member one said......
"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 yes is your head light switch (that rotates to turn on the dome light with the doors closed) working?
"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 yes is your head light switch (that rotates to turn on the dome light with the doors closed) working?
Also check that your dome light bulb itself is good. The aftermarket companys offer replacement LED bulbs and new plastic covers as the old covers all have melted or crumbled by now from the heat of those bulbs.
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