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Old 01-12-2014, 01:40 PM   #1
cool68
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Interior Dome Light Wiring - '68 C10

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?
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Old 01-12-2014, 02:24 PM   #2
VetteVet
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Re: Interior Dome Light Wiring - '68 C10

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.


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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.



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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.


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Old 01-14-2014, 12:25 PM   #3
cool68
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Re: Interior Dome Light Wiring - '68 C10

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?
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Old 01-14-2014, 02:20 PM   #4
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Re: Interior Dome Light Wiring - '68 C10

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.

Quote:
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.
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Old 01-15-2017, 08:00 PM   #5
cpnbnanamn
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Re: Interior Dome Light Wiring - '68 C10

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..
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Old 01-15-2017, 08:32 PM   #6
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Re: Interior Dome Light Wiring - '68 C10

If I'm reading the diagram correctly, it's activated by the headlight switch?
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Old 01-15-2017, 11:30 PM   #7
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Re: Interior Dome Light Wiring - '68 C10

Quote:
Originally Posted by cpnbnanamn View Post
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.

Quote:
Originally Posted by cpnbnanamn View Post
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.
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Old 01-16-2017, 11:19 AM   #8
cpnbnanamn
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Re: Interior Dome Light Wiring - '68 C10

Thanks, Ray!
Figured out why it wasn't coming on. The knob just spins on the shaft. Guess it's time to replace it!!
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Old 04-05-2017, 04:48 PM   #9
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Re: Interior Dome Light Wiring - '68 C10

Quote:
Originally Posted by VetteVet View Post
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?
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Old 04-05-2017, 05:50 PM   #10
VetteVet
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Re: Interior Dome Light Wiring - '68 C10

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.


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