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Dome lights not working

'76 Carrera, the two dome lights are not working. New bulbs. Trunk light works.
These dome lights are rocker type so it is not door dependent. I rocked the lights and they did not come on.
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Old 11-01-2017, 02:33 PM
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Quote:
Originally Posted by bcgreen View Post
'76 Carrera, the two dome lights are not working. New bulbs. Trunk light works.
These dome lights are rocker type so it is not door dependent. I rocked the lights and they did not come on.
Do the lights come on with the door switch? If so, but they do not light with the door closed, they probably are not grounded to the chassis frame. The light fixtures are grounded to the metal frame of the car by a metal nub that contacts the frame. Sometimes the headliner material gets caught between the fixture and the metal frame, insulating the fixture and preventing the fixture from lighting when rocked to the ON position.

If the lights do not light under any conditions, check for power at each fixture (black wire) and for ground at brown wire with the door open. Also, check that the brown wire is connected to the correct terminal.
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Old 11-01-2017, 03:22 PM
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Quote:
Originally Posted by ossiblue View Post
Do the lights come on with the door switch? If so, but they do not light with the door closed, they probably are not grounded to the chassis frame. The light fixtures are grounded to the metal frame of the car by a metal nub that contacts the frame. Sometimes the headliner material gets caught between the fixture and the metal frame, insulating the fixture and preventing the fixture from lighting when rocked to the ON position.

If the lights do not light under any conditions, check for power at each fixture (black wire) and for ground at brown wire with the door open. Also, check that the brown wire is connected to the correct terminal.
Do not come on with the door closed, or open. Will reseat the light just in case it isn't contacting the frame.
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Old 11-01-2017, 03:55 PM
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Old 11-01-2017, 05:03 PM
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Check for power at the black wire. Use a test light. If power, test to see if the brown wire is grounded with door button pushed in. If both check out, reconnect to light, close door, and rock the fixture through all its stops. Light should come on in one position while not installed into door frame.
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Old 11-01-2017, 05:57 PM
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If you haven't noticed but I am electrically challenged. I disconnected the light fixture so I would work with just the wires. I am using a multimeter and turned the dial to VDCV and attached the red lead to the black wire and the black lead to the frame of the window and get fluctuation readings from 136 - 170. I don't understand why the fluctuation.
Aside note - on the passenger side the wires are reversed from the driver's side.
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Old 11-01-2017, 06:57 PM
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On my 87 the interior light has a ground wire running from the light center tab to a ground tab above the light.

Old 11-01-2017, 07:52 PM
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It looks like you have the wires connected to the wrong terminals.

The black wire should be connected to the other side--where the brown wire now is. It is the ground connection that is controlled by the switching mechanism of the fixture, the end where the white insulating material is. The black wire should be on the single, non moving terminal that is not touching the metal body of the fixture in any way. You need to switch your wires.

Look at the picture posted by HaroldMHedge. The brown/white wire comes from the door switch, a ground. The black is power and is connected to the single, non moving terminal. He also has a ground wire that you don't have, or need, as long as the fixture body makes contact with the door frame. If you look at the far right of his picture, you'll see a piece of spring metal attached to the fixture by a " [ " shaped bracket. That spring piece holds the fixture into the frame and also makes a ground contact. The other side is held in by the ridges on the white insulation. Your light fixture has the bracket, but not the piece of spring metal. That's likely why it doesn't light at all with the door closed.

You can always add a separate ground wire and connect it to the fixture body if you wish. Something to consider if you cannot find the spring metal that fits to the fixture.
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Last edited by ossiblue; 11-02-2017 at 08:13 AM..
Old 11-01-2017, 08:52 PM
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While you're in there, it might be a good time to consider LED lighting for those dome lights.

https://www.superbrightleds.com/vehicle?reset=1

Just a thought, no affiliation
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Old 11-01-2017, 10:02 PM
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The black wire should be connected to the other side--where the brown wire now is. It is the ground connection that is controlled by the switching mechanism of the fixture, the end where the white insulating material is. The black wire should be on the single, non moving terminal that is not touching the metal body of the fixture in any way. You need to switch your wires.

Look at the picture posted by HaroldMHedge. The brown/white wire comes from the door switch, a ground. The black is power and is connected to the single, non moving terminal. He also has a ground wire that you don't have, or need, as long as the fixture body makes contact with the door frame. If you look at the far right of his picture, you'll see a piece of spring metal attached to the fixture by a " [ " shaped bracket. That spring piece holds the fixture into the frame and also makes a ground contact. The other side is held in by the ridges on the white insulation. Your light fixture has the bracket, but not the piece of spring metal. That's likely why it doesn't light at all with the door closed.

You can always add a separate ground wire and connect it to the fixture body if you wish. Something to consider if you cannot find the spring metal that fits to the fixture.


I noticed that ground wire but thought since my vehicle is a '76 that by '87 this was an improvement by Porsche, but failed to notice my fixture has the connection for the ground wire. My fixture fits into the frame securely and thought it is making contact with the frame. I will look into finding the spring metal and make a ground wire.
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Last edited by bcgreen; 11-02-2017 at 09:05 AM..
Old 11-02-2017, 08:40 AM
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Quote:
Originally Posted by sky1jord View Post
While you're in there, it might be a good time to consider LED lighting for those dome lights.

https://www.superbrightleds.com/vehicle?reset=1

Just a thought, no affiliation
I have the LEDs on my instruments. Will consider them for the dome once I get them working. I just wish they made LEDs for turn signals.
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Old 11-02-2017, 08:44 AM
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Quote:
Originally Posted by bcgreen View Post
The black wire should be connected to the other side--where the brown wire now is. It is the ground connection that is controlled by the switching mechanism of the fixture, the end where the white insulating material is. The black wire should be on the single, non moving terminal that is not touching the metal body of the fixture in any way. You need to switch your wires.

Look at the picture posted by HaroldMHedge. The brown/white wire comes from the door switch, a ground. The black is power and is connected to the single, non moving terminal. He also has a ground wire that you don't have, or need, as long as the fixture body makes contact with the door frame. If you look at the far right of his picture, you'll see a piece of spring metal attached to the fixture by a " [ " shaped bracket. That spring piece holds the fixture into the frame and also makes a ground contact. The other side is held in by the ridges on the white insulation. Your light fixture has the bracket, but not the piece of spring metal. That's likely why it doesn't light at all with the door closed.

You can always add a separate ground wire and connect it to the fixture body if you wish. Something to consider if you cannot find the spring metal that fits to the fixture.


I noticed that ground wire but thought since my vehicle is a '76 that by '87 this was an improvement by Porsche. My fixture fits into the frame securely and thought it is making contact with the frame. I will look into finding the spring metal and make a ground wire.
You're correct in that the ground wire was a later improvement. Lights on cars earlier than yours didn't have the spring clip, they just had a metal nub protruding from the fixture that made contact with the door frame. Your light is an improvement over that earlier type.

At this point, I suggest you disconnect the wires from both lights, and test to see if the black wire has power. Again, use a test light. If the test light glows when connected to black and ground, you're half-way there. Test the brown wire for ground, with the door button pushed in, by connecting the test light to the black wire and also the brown wire. If it lights, your door/ground connection is good. With that out of the way, connect the wires back into each fixture with the brown wire on the side that switches/white insulator, and open a door. Rock the light through it's stops and it should light.
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Old 11-02-2017, 09:14 AM
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Quote:
Originally Posted by ossiblue View Post
You're correct in that the ground wire was a later improvement. Lights on cars earlier than yours didn't have the spring clip, they just had a metal nub protruding from the fixture that made contact with the door frame. Your light is an improvement over that earlier type.

At this point, I suggest you disconnect the wires from both lights, and test to see if the black wire has power. Again, use a test light. If the test light glows when connected to black and ground, you're half-way there. Test the brown wire for ground, with the door button pushed in, by connecting the test light to the black wire and also the brown wire. If it lights, your door/ground connection is good. With that out of the way, connect the wires back into each fixture with the brown wire on the side that switches/white insulator, and open a door. Rock the light through it's stops and it should light.
Okay, finally got out to the car to do the recommended test. Bought a test light from HF and checked it at the battery and it is functional. Disconnected wires from both lights and tested the black wire for power - No Power. I did have a light on in the trunk when I started. I took the cover off the fuse box to see which fuse controls the interior lights and in my vehicle it is the first fuse, the fuse closest to the firewall. The first two fuses, the test light lit up, but the others down the line did not.

The other dome light does have the spring. The other one without the spring does not have the cross member that holds the spring. Will see what I can rig up once I figure out how to get power to the dome.
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Last edited by bcgreen; 11-07-2017 at 12:17 PM..
Old 11-07-2017, 11:34 AM
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Looking at the wiring in the passenger side there are a number of wires taped off and one with some sort of connector. The spotted black wire has power but I did not find any power coming from the plastic connector.



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Old 11-07-2017, 03:44 PM
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Quote:
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Looking at the wiring in the passenger side there are a number of wires taped off and one with some sort of connector. The spotted black wire has power but I did not find any power coming from the plastic connector.



If the black spotted wire has power, then so does the solid black that it is joined with at the thing next to the grey wire. Is that a connector?

Does the black/spotted wire lead to the trunk light? If so, then the connector (?) they have in common is supposed to feed to the interior lights.

Before you do anything else, let us know the following:

Is the trunk light working?

Is the clock working (or have power)?

Is the glove box light working (or have power)?

My guess is the loose connector on top of the grey wire is the feed to the interior lights, but not sure without a 77 diagram. On the 78 diagram, the clock and glove box light are powered before the connector to the trunk light, so if yours is the same, you should have power to the clock, glove light, and trunk light. The ignition buzzer is also connected to the same feed as the interior lights, which could be the loose connector in your photo. Does the ignition warning buzzer work?
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Last edited by ossiblue; 11-07-2017 at 05:38 PM..
Old 11-07-2017, 05:28 PM
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Should be single male connectors under the tape. (Black and brown)
They connect to the corresponding colored wires coming from the interior dome lamps coming down from the A pillar.
Black/White goes to the hood lamp.
Ignition buzzer circuit ties in to the plastic connector.
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Last edited by timmy2; 11-07-2017 at 08:22 PM..
Old 11-07-2017, 08:18 PM
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If the black spotted wire has power, then so does the solid black that it is joined with at the thing next to the grey wire. Is that a connector?

Does the black/spotted wire lead to the trunk light? If so, then the connector (?) they have in common is supposed to feed to the interior lights.

Before you do anything else, let us know the following:

Is the trunk light working?

Is the clock working (or have power)?

Is the glove box light working (or have power)?

My guess is the loose connector on top of the grey wire is the feed to the interior lights, but not sure without a 77 diagram. On the 78 diagram, the clock and glove box light are powered before the connector to the trunk light, so if yours is the same, you should have power to the clock, glove light, and trunk light. The ignition buzzer is also connected to the same feed as the interior lights, which could be the loose connector in your photo. Does the ignition warning buzzer work?


The spotted wire is spliced to a solid black wire leading up to the trunk light.

The trunk light has power.

The connector does not have power.

The glove compart. has power.

The clock has power as does the instrument panel.

No ignition buzzer. Perhaps they didn't produce a buzzer for the ignition in 1976, maybe that was an USA thing.
A better look at the connector.



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Old 11-08-2017, 11:35 AM
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Ignore the clear connector, you don’t have that option.
Black and brown wires with open connection points connect to the corresponding colored wires coming down from the A pillar.
(Male to female as appropriate.)
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Old 11-08-2017, 11:52 AM
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Ignore the clear connector, you donít have that option.
Black and brown wires with open connection points connect to the corresponding colored wires coming down from the A pillar.
(Male to female as appropriate.)
Are you saying to connect the two pairs of wires that are wrapped in electrical tape?



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Old 11-09-2017, 08:40 AM
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Find the 2 wires coming down from the A pillar, one will be black and one will be brown.
Have you located those yet?

Connect the black wire from the A pillar to the black wire that is currently taped.
Connect the brown wire from the A pillar to the brown wire that is currently taped

Dome lights should now work barring any other problems in the wiring to them.
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Old 11-09-2017, 10:03 AM
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