Interior Dome Light Wiring - '68 C10

[cool68]

light not working at first, even with new dome light set up and wiring. now both wires - orange/white - have constant power - does not change when turning lights knob. power does go off when turning headlights/parking lights on. think that orange wire was the power wire but, do not know what white wire is for. any ideas, input?

[VetteVet]

The orange wire is the power wire and has constant power to the dome light. It runs from the fuse panel to the headlight switch for tail light power and it also runs from the fuse panel to the stop light switch for the brakes. The power for the dome light runs from the fuse panel down under the drivers side sill plate and up to the dome light.

The white wire is the grounding side of the circuit and it runs from the headlight switch down to the harness to the drivers side door switch and under the sill plate back up to the dome light. There should be a junction with another white wire that runs over to the passenger side door switch as well.

Follow the orange wire at the light switch and the white wire is just below it.

Ignore any arrows they are for other stuff.







This is the orange wire feeds from the fuse panel, The large red wire feeds the orange wire which is fused and then feeds the brake switch, the headlight switch, and the dome light. These are not key on power.






This is the wiring to the dome light and the rear lighting. The fuel sender goes under the sill plate too but the tailight wires run under the truck cab along the frame.

[cool68]

Thanks for info. do not have door jamb dome light switches. when I put bulb in dome light socket the white wire becomes a constant hot wire - electricity flowing - bulb does not work. checked bulb with wire jumpers at battery and bulb works properly. guessing there is problem at headlight switch? turning knob to left to activate bulb does not turn on dome light. thinking of just installing a basic on/off switch - cutting white wire and put bulb side of wire to one connector and just installing a direct ground wire to other. will work? any other ideas?

[VetteVet]

The orange wire is the hot wire. The white wire is the ground wire. If the white wire is not grounded and you put the bulb in the socket the power from the orange wire flows through the bulb and into the white wire making it hot. The bulb will not light until it has a path to ground for the electrons in the circuit.

The whit wire grounds at the headlight switch when the know is turned all the way CW.
Your headlight switch may not be grounded or the white wire may have a break in it.
Put the bulb back in and run a jumper from the bulb socket to a good ground and the light should come on.

thinking of just installing a basic on/off switch - cutting white wire and put bulb side of wire to one connector and just installing a direct ground wire to other. will work? any other ideas?

Do this,---Get a multimeter and check the orange wire at the light socket for 12 volts between the orange wire connection and ground.
Then put the meter on resistance and check the white wire at the light socket for zero ohms between the white wire connection and a good ground. You should get zero ohms, if not the white wire is not grounded and the light will not work, remember the light switch knob has to be all the way to the left.

I don't like to see work arounds like you're contemplating, When the fix is easy. It can create more problems. All you are going to do is switch the white wire to ground just like the headlight switch does.

[cpnbnanamn]

So, being pretty new to these trucks, I have a stupid question... Do these trucks really not have a door jamb switch for the dome light? I have a '67, and the dome light isn't working, and I know the bulb is good. Not really sure where to start. I'm good at troubleshooting, just need to know more about the electrical system in it..

[cpnbnanamn]

If I'm reading the diagram correctly, it's activated by the headlight switch?

[ray_mcavoy]

Originally Posted by cpnbnanamn

If I'm reading the diagram correctly, it's activated by the headlight switch?

Yes, rotating the headlight knob all the way counterclockwise should close the contacts that ground the white wire and turn on the dome light. Rotating the knob also varies the brightness of the instrument panel lights.

Originally Posted by cpnbnanamn

Do these trucks really not have a door jamb switch for the dome light?

Door jamb switches were not standard issue in these trucks. I believe they may have been available as an option and/or part of some of the upper level trim packages.

You can add door jamb switches if desired by connecting them to the existing white wire. That way, the dome light will come on when any one of the switches grounds that wire.

[cpnbnanamn]

Thanks, Ray!
Figured out why it wasn't coming on. The knob just spins on the shaft. Guess it's time to replace it!!

[wolfsden]

Originally Posted by VetteVet

The orange wire is the hot wire. The white wire is the ground wire. If the white wire is not grounded and you put the bulb in the socket the power from the orange wire flows through the bulb and into the white wire making it hot. The bulb will not light until it has a path to ground for the electrons in the circuit.

The whit wire grounds at the headlight switch when the know is turned all the way CW.
Your headlight switch may not be grounded or the white wire may have a break in it.
Put the bulb back in and run a jumper from the bulb socket to a good ground and the light should come on.



Do this,---Get a multimeter and check the orange wire at the light socket for 12 volts between the orange wire connection and ground.
Then put the meter on resistance and check the white wire at the light socket for zero ohms between the white wire connection and a good ground. You should get zero ohms, if not the white wire is not grounded and the light will not work, remember the light switch knob has to be all the way to the left.

I don't like to see work arounds like you're contemplating, When the fix is easy. It can create more problems. All you are going to do is switch the white wire to ground just like the headlight switch does.

What color wire in the back of the rotating switch would the white wire from the dome light be hooked up to?

[VetteVet]

According to the diagrams in post 2, the wire is an 18 ga. white wire. This diagram has a blue arrow pointing to the connection on the headlight switch.

If you count 10 wires up from the bottom of the first and second diagrams and match them you'll see that the second diagram shows the 18ga white wire runs from the headlight switch to the dome light fuse on the fuse panel.

[slowboy]

Originally Posted by VetteVet

The orange wire is the hot wire. The white wire is the ground wire. If the white wire is not grounded and you put the bulb in the socket the power from the orange wire flows through the bulb and into the white wire making it hot. The bulb will not light until it has a path to ground for the electrons in the circuit.

The whit wire grounds at the headlight switch when the know is turned all the way CW.
Your headlight switch may not be grounded or the white wire may have a break in it.
Put the bulb back in and run a jumper from the bulb socket to a good ground and the light should come on.



Do this,---Get a multimeter and check the orange wire at the light socket for 12 volts between the orange wire connection and ground.
Then put the meter on resistance and check the white wire at the light socket for zero ohms between the white wire connection and a good ground. You should get zero ohms, if not the white wire is not grounded and the light will not work, remember the light switch knob has to be all the way to the left.

I don't like to see work arounds like you're contemplating, When the fix is easy. It can create more problems. All you are going to do is switch the white wire to ground just like the headlight switch does.

I'm very sorry for asking on this thread but I'm having dome light problems and this is all I can find about it.
Both my orange wire 'and' white wire at my dome light have voltage. At least they both light up my voltage light. It doesn't matter if I have my headlight switch turned all the way to ground. Are both of these wires supposed to have constant voltage no matter where the headlight switch is turned to?
I didn't think the white wire would do anything until switch is turned to the ground position.
Again sorry for high jacking your thread!

Keith

[dmjlambert]

As VetteVet mentions "The white wire is the grounding side of the circuit and it runs from the headlight switch down to the harness to the drivers side door switch and under the sill plate back up to the dome light. "

If you connect the white wire to ground the dome light will light up. So, I think the things you mention are correct, such as "I didn't think the white wire would do anything until switch is turned to the ground position."

There are a couple methods grounding the white wire happen. One is if your headlight switch is rotated all the way counterclockwise you will feel a detent and the dome light comes on. This is assuming the headlight switch is installed and has a good switch body to cab ground connection. Another way is if your truck is equipped with switches in the door jambs, those have a single wire going to them and the jamb switch shorts the wire to ground. I found it necessary to remove my jamb switches and clean the contact surfaces with a wire brush to get them working.

You will notice a voltage on the white wire if it is not grounded. So you're headlight switch is either not grounded, or the dome light switch in it is not working, or I think the most likely thing you have going on is a connection at a switch or at a connector is not good and clean and connected. Check all the connectors and clean them up and plug them in again. It is possible when a connector is pushed onto a switch or into another connector, the terminal inside the connector may pop out of the back of the connector. So inspect for that sort of thing happening and re-seat terminal if necessary.

[dmjlambert]

One more thing to mention, if you happen to have LED light bulbs, they are usually polarity dependent, they will work in the socket one orientation and not work in the opposite orientation. I suggest use regular incandescent light bulbs. There's a reason we don't hear from many of the LED bulb users here on the forum after their initial few posts trying to get LEDs to work. They are now living in insane asylums with no wi-fi and playing checkers with perl CGI programmers.

[RustyPile]

Originally Posted by dmjlambert

<<<<<snip>>>>> I suggest use regular incandescent light bulbs. There's a reason we don't hear from many of the LED bulb users here on the forum after their initial few posts trying to get LEDs to work. They are now living in insane asylums with no wi-fi and playing checkers with perl CGI programmers.

A truer statement was never spoken....

[slowboy]

Originally Posted by dmjlambert

As VetteVet mentions "The white wire is the grounding side of the circuit and it runs from the headlight switch down to the harness to the drivers side door switch and under the sill plate back up to the dome light. "

If you connect the white wire to ground the dome light will light up. So, I think the things you mention are correct, such as "I didn't think the white wire would do anything until switch is turned to the ground position."

There are a couple methods grounding the white wire happen. One is if your headlight switch is rotated all the way counterclockwise you will feel a detent and the dome light comes on. This is assuming the headlight switch is installed and has a good switch body to cab ground connection. Another way is if your truck is equipped with switches in the door jambs, those have a single wire going to them and the jamb switch shorts the wire to ground. I found it necessary to remove my jamb switches and clean the contact surfaces with a wire brush to get them working.

You will notice a voltage on the white wire if it is not grounded. So you're headlight switch is either not grounded, or the dome light switch in it is not working, or I think the most likely thing you have going on is a connection at a switch or at a connector is not good and clean and connected. Check all the connectors and clean them up and plug them in again. It is possible when a connector is pushed onto a switch or into another connector, the terminal inside the connector may pop out of the back of the connector. So inspect for that sort of thing happening and re-seat terminal if necessary.

Thanks for the reply!
I had the headlight switch just hanging down in front of the dash, not mounted to the dash... as you mentioned the "headlight switch is installed and has a good switch body to cab ground connection". It was not grounded to body.
Once I mounted the headlight switch to the dash it apparently made the needed ground and now my dome and cargo lights are working.
Thanks again!
Keith

[slowboy]

Originally Posted by RustyPile

A truer statement was never spoken....

I have new incandescent light bulbs in my cluster and can't hardly see the speedometer numbers.

[slowboy]

Originally Posted by dmjlambert

One more thing to mention, if you happen to have LED light bulbs, they are usually polarity dependent, they will work in the socket one orientation and not work in the opposite orientation. I suggest use regular incandescent light bulbs. There's a reason we don't hear from many of the LED bulb users here on the forum after their initial few posts trying to get LEDs to work. They are now living in insane asylums with no wi-fi and playing checkers with perl CGI programmers.

I have new incandescent light bulbs in my cluster and can't hardly see the speedometer numbers.

[dmjlambert]

You can probably make sure the brightness is turned up, and try 168 bulbs to replace 194 if necessary. That's what I would do. Also clean up the ground connection for the instrument cluster, and clean up the printed circuit where the bulb holder contacts the circuit and where the plug fits in the circuit. I used Brasso to get the metal nice and shiny.

Edit -- Adding hardly see the speedometer numbers is sometimes caused by aftermarket lenses that are printed incorrectly. There is a thread here on the forum where it was discussed the lenses being done wrong. So if you have a new lens that could be the problem. https://www.67-72chevytrucks.com/vbo...d.php?t=813854