Interior light

[easyrider]

I have power on both sides of bulb wires orange and white, so when attached nothing happens. When either wire is set to bulb and other side of bulb is run to ground it burns. New wiring harness and this is only problem I've had. Any suggestions?

[Richard]

The bulb will show +12v on either side. The circuit is always hot. It is switched to ground. Pull the bulb, then check voltage. Which ever wire is not hot is the switch to ground side.

[easyrider]

The orange wire is not grounded for some reason., so would it hurt if I ran a ground wire to this wire?

[Richard]

The wire that does not have 12v is SWITCHED to ground. If it was grounded all the time the light would be on all the time. If your truck has door pins it should ground when doors are open. Also rotating the headlight switch to turn light on would cause it to ground.

[RustyPile]

Originally Posted by easyrider

The orange wire is not grounded for some reason., so would it hurt if I ran a ground wire to this wire?

If you don't have a detailed wiring diagram for your truck, go to the ELECTRICAL FORUM on this site and download the wiring diagram for your truck..

The following is a very detailed and highly simplified description of how the dome light circuit works.

If your new harness is color coded correctly and matches the original color code, the orange wire comes from a fuse in the fuse box. It's always hot, and probably branches off and provides feed voltage for more than one circuit, but it provides 12V on one of the terminals on the dome light.. DO NOT GROUND THIS WIRE!! Fuses will blow.. The other terminal on the dome light should have a white wire connected to it IF the harness follows the original color coding. This is the wire that goes to a grounding switch, thus the term "switched to ground"... One of the switches used for this purpose is the headlight switch.. When the headlight switch knob is twisted CCW to the stop, the ground side is completed and the dome light comes on.. On some models (not all) of our trucks, push button grounding switches are installed in the A pillar between the hinges.. The white wire is connected to these switches and when a door is opened, the switch connects to ground and the dome light comes on....

[easyrider]

Well, i beat my head against truck door for a couple hours with this. I tested wires from fuse box (orange and white) and there are two orange wires run into plug and one white wire and they plug into wire to interior light. The wiring harness is m & h and everything seems to work well. But, my white wire is hot and the orange wires don't complete the circuit. I don't know about why, but that is the way it is, so i have to go with it. I'm not getting a ground when i rotate the light switch all the way to left till i feel the indent. I can ground the light at bulb and it will burn, so i know my problem is with ground switching. Does the light switch have to be mounted and grounded? I'm not getting anything from orange wires. And, would i be experincing this problem if my headlight switch was bad? It's new but doesn't mean it's working correctly. This should have been relatively simple but its turn into a nightmare. Thank you for letting me pick your brain.

[Richard]

Originally Posted by easyrider

Well, i beat my head against truck door for a couple hours with this. I tested wires from fuse box (orange and white) and there are two orange wires run into plug and one white wire and they plug into wire to interior light. The wiring harness is m & h and everything seems to work well. But, my white wire is hot and the orange wires don't complete the circuit. I don't know about why, but that is the way it is, so i have to go with it. I'm not getting a ground when i rotate the light switch all the way to left till i feel the indent. I can ground the light at bulb and it will burn, so i know my problem is with ground switching. Does the light switch have to be mounted and grounded? I'm not getting anything from orange wires. And, would i be experincing this problem if my headlight switch was bad? It's new but doesn't mean it's working correctly. This should have been relatively simple but its turn into a nightmare. Thank you for letting me pick your brain.

'
RustyPile did a a bit better explaining than I did. Have you tried touching the switch to body while rotated to the on postion? Have not looked at wiring diagram in some time and do not know if switch has a ground wire.

[RustyPile]

Originally Posted by easyrider

Well, i beat my head against truck door for a couple hours with this. I tested wires from fuse box (orange and white) and there are two orange wires run into plug and one white wire and they plug into wire to interior light. The wiring harness is m & h and everything seems to work well. But, my white wire is hot and the orange wires don't complete the circuit. I don't know about why, but that is the way it is, so i have to go with it. I'm not getting a ground when i rotate the light switch all the way to left till i feel the indent. I can ground the light at bulb and it will burn, so i know my problem is with ground switching. Does the light switch have to be mounted and grounded? I'm not getting anything from orange wires. And, would i be experincing this problem if my headlight switch was bad? It's new but doesn't mean it's working correctly. This should have been relatively simple but its turn into a nightmare. Thank you for letting me pick your brain.

No need to be picking and probing around the fuse box because you have voltage at the dome light..As someone has already told you, the white wire is not a hot wire, but will have voltage on it IF only if the bulb is in place.. By whatever means, when the white wire is grounded, the dome light will come on.. The headlight is a grounding switch for the dome light. It has to be mounted in the dash or a jumper clamped to the metal housing and a suitable ground point. The dome light will come on when the knob is twisted.. Turn the knob past the detent a small amount more to reach the stop.. There are other white wires in the body harness - a white wire is used to connect the brake light switch to the turn signal switch.. Do not confuse these two circuits.. If the dome light doesn't come on then do the following test.

The following test will test the complete dome light circuit ----- You say one of the terminals of the dome light has voltage on it.. Install the bulb, and be sure the two wires' (white and orange) plugs near the fuse box are plugged into each other.. ... There is only one white wire on the headlight switch plug.. Using a jumper, clip one end to the white wire at the headlight switch.. touch the other end of the jumper to a suitable ground, the E-brake bracket is a good ground point.. The dome light should come on.. If it doesn't, there is probably an open in it between the dome light terminal and the headlight switch plug...

[easyrider]

Thanks for all the helpful advice. I had worked at it for so long i had forgot what i had tried and what i had not. So this moning i tackled it all again. This time with a clearer mind and it turns out all that you told me was right and i had created this monster! I found when i ran a jumper to the headlight switch and grounded it everything worked.....one step i had overlooked was to mount the headlight switch..i still don't know why i had voltage on the white wire, since it only goes to a ground on the headlight switch, but i did unless in all my confusion i simply just lost my logical mind..which is highly possible with all the stress assembling this truck with aftermarket parts..thanks again for keeping this process sane....

[RustyPile]

Originally Posted by easyrider

Thanks for all the helpful advice. I had worked at it for so long i had forgot what i had tried and what i had not. So this moning i tackled it all again. This time with a clearer mind and it turns out all that you told me was right and i had created this monster! I found when i ran a jumper to the headlight switch and grounded it everything worked.....one step i had overlooked was to mount the headlight switch..i still don't know why i had voltage on the white wire, since it only goes to a ground on the headlight switch, but i did unless in all my confusion i simply just lost my logical mind..which is highly possible with all the stress assembling this truck with aftermarket parts..thanks again for keeping this process sane....

I'm responding to the highlighted part of your post.. Easyrider, you still don't have a thorough understanding of how electricity works.. But keep at it, you're getting there.. A battery has 2 posts for a reason.. For an electrical circuit to be complete, the electrons have to flow from the battery out to the load (bulb, relay, motor, sensor, gauge, etc) and then make a return trip back to the battery,, The return trip is referred to as "the ground path".. In most cases, the ground path on a vehicle is the body/frame itself. That's why everyone preaches so loudly about having a good ground connection.

The dome light housing in our trucks is made of plastic - a non-conducting material.. So the ground path has to be through a wire.. Voltage is applied through the orange wire to one "post" of the bulb.. Voltage passes through the bulb's filament and into the white wire.. In your case, when the headlight switch is NOT turned to the on position for the dome light, voltage can be measured on the white wire because the voltage doesn't "stop" at the bulb, it passes through it.. When the white wire is grounded and the bulb turns on, all current is absorbed by the bulb and cannot be read on the ground side.. A good way to illustrate this is to connect one test lead of a voltmeter to the white wire at the bulb.. Connect the other lead to a good ground point.. With the dome light turned off, you can read 12V.. Twist the headlight switch to turn on the dome light.. The voltmeter will now read Zero volts, yet the light is in full brightness..

Before all you engineer types chime in and "correct" some of my description, I fully understand the direction taken by current flow or more correctly, electron flow.. I am trying my best to simplify this for someone who is not knowledgeable enough to understand the physics side of electrcity...