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John
John, ASE Master Technician
Category: Car
Satisfied Customers: 608
Experience:  ASE Certified Master Technician, ASE Certified Service Consultant, 22 years professional experience
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my four head dome interior lights wont turn on and they have

This answer was rated:

my four head dome interior lights wont turn on and they have power on both sides

John :

Hello. I don't see what type of vehicle we are working on here, for some reason the information is not there but I believe I can help you. Typically, if you have power on both sides of the light assembly that tells you that there is power to the light and that the bulb is good since it can carry the voltage through it. What you are missing is the ground supplied to the circuit. If you have a wiring diagram for the car we can track down where the ground is for the system, or you could supply a new ground. Just be sure to add the ground on the ground side of the light, not on the power supply side. Again, I am sorry I can't give you more information without the vehicle information. But this symptom is common in electrical circuits.

John :

It is possible (and perhaps likely) that the ground is switched in the system and supplying a ground will only cause the lights to stay on all the time. We probably don't want that.

Customer:

Sorry the vehicle is 1994 pontic grand am v6 3.1L 4 door se

John :

Ok, let me pull up some info

John :

The white wires are the ground side, orange wires are the power side.

Customer:

ok

John :

Do you have a sunroof?

Customer:

nope

John :

Ok, do the wire colors sound correct (options in the vehicle change some wire colors)

Customer:

yes

John :

Good.

John :

Wiring diagram does not show me the whole system ... still looking

Customer:

ok

John :

Here is the description of how the system works:

John :

The Headlight Switch controls the sustained illumination feature for the Courtesy Lights. After all the doors are closed, the Headlight Switch will keep the Courtesy Lights ON for approximately 16 seconds , gradually dimming the lights until they are OFF. Energizing the Power Door "UNLOCK," with either the key fob or the Door Lock Switch, will also trigger the sustained illumination feature. If the Ignition Switch is turned "ON," the sustained illumination will be defeated, overriding the Power Door "UNLOCK" input. The Remote Door "LOCK" input from the Keyless Entry Receiver will also defeat the sustained illumination feature.

Customer:

ok

John :

Reading that, I think the headlight switch may be faulty since it controls the ground to the dome lights as it describes above. I think the internal circuit that runs out to the dome lights has failed inside the switch.

John :

Seems a bit unusual to me.

Customer:

the dimmer switch or the light switch for the turn singles?

Customer:

and i know the ground for them is the G300

Customer:

which is under the drivers seat

John :

I believe they call it a Headlight Combination switch, so that would be the one with the turn signals.

Customer:

ok that also have the cruise control on it

John :

You can test it by supplying a ground to the white wire either at the headlight switch or at the dome lights.

John :

Yep, that's the one.

Customer:

ok

Customer:

but do you thin that i should take a look at the ground underneath the drivers seat?

John :

The ground under the drivers seat (G300) supplies a ground to that switch, the problem is the switch is not passing the ground through the internal timer to the dome light circuit.

John :

If the other components on that switch are working then I that ground is ok.

John :

Have you seen the dome lights work before?

Customer:

no but i am the third owner of the car

Customer:

and the cruise and turn singles work fine so would it not be the switch then?

John :

The switch is only faulty on the internal circuit that controls the dome light timer. Other functions in the switch can still work ok.

John :

It is possible that the wire that runs between the dome lights and the headlight switch has been cut or damaged.

Customer:

ok

John :

Will you try to perform this repair yourself?

Customer:

i am an apprentice so probably if i get time and help of one of the licensed tech then yea i will

Customer:

but i will also have to get the part frist

John :

Ok, you might want to check that white wire at the switch before you replace it. If it grounds then the wire is broken somewhere between the switch and the dome light (I know it runs through connector C200). If it does not ground then the switch is your problem.

John :

Anything else I can help you with?

Customer:

nope that is all thank you very much

Customer:

one last thing actually

Customer:

what if say wire is broken

Customer:

what would happen if i created my own ground for it?

John :

If you make your own ground then the lights will always be on.

John :

You could wire in your own switch to ground.

Customer:

ok

Customer:

thank you again

John :

glad to help

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