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I'm trying to get the dome lights working on a 1976 Avanti. I've got the Bob Johnstone wiring diagram.

I pulled the driver's door switch and found a red/white wire with 12v connected to the switch and a heavy white wire, that seemed to be a ground, connected to nothing.

I also pulled the passenger side switch and found a 12v red/white wire only. Where does this circuit get it's ground??

Any help will be greatly appreciated,.

thanx

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Just trying to think along with you, I don't claim any expertise...

On the Stude Avanti the white wires at the dome lights provide ground, the black wires provide power.

The Stude Avanti passenger side dome light connects to the same ground wire that connects to the cigar lighter (and other devices).

The driver-side dome light ground wire connects to the same white ground wire that runs to the driver-side tail light.

I doubt that changed in 70's Avanti II's.

Are your tail lights working?

A red & white wire connects across from the door switch on the left to the door switch on the right.

Both door switches should have a white wire attached to their second terminal, so that IS a problem on your car.

It appears to me (on a Stude) that the door switches block current to the dome/courtesy lights, but block it ONLY when BOTH door switch buttons are depressed.

You might check continuity across the contacts/terminals on both door switches with & without the buttons depressed (you should NOT have continuity when the button is depressed).

Do you know if you have power to the rear courtesy (left & right dome) lamps with the doors open? (probably not, since the white wire at one switch is not attached)

Have you checked for power and a good ground at the courtesy lamp bulb sockets?

Once when I was chasing an electrical issue, I found the electrical diagram in the service manual hard to read (and trace with my fingers) so I scanned it and enlarged the scan,

divided it into quarters, and printed it, then taped the parts together again to get one big drawing.... probably FEDEX or a good print shop could do an even better job of enlarging it.

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Just trying to think along with you, I don't claim any expertise...

On the Stude Avanti the white wires at the dome lights provide ground, the black wires provide power.

The Stude Avanti passenger side dome light connects to the same ground wire that connects to the cigar lighter (and other devices).

The driver-side dome light ground wire connects to the same white ground wire that runs to the driver-side tail light.

I doubt that changed in 70's Avanti II's.

Are your tail lights working?

A red & white wire connects across from the door switch on the left to the door switch on the right.

Both door switches should have a white wire attached to their second terminal, so that IS a problem on your car.

It appears to me (on a Stude) that the door switches block current to the dome/courtesy lights, but block it ONLY when BOTH door switch buttons are depressed.

You might check continuity across the contacts/terminals on both door switches with & without the buttons depressed (you should NOT have continuity when the button is depressed).

Do you know if you have power to the rear courtesy (left & right dome) lamps with the doors open? (probably not, since the white wire at one switch is not attached)

Have you checked for power and a good ground at the courtesy lamp bulb sockets?

Once when I was chasing an electrical issue, I found the electrical diagram in the service manual hard to read (and trace with my fingers) so I scanned it and enlarged the scan,

divided it into quarters, and printed it, then taped the parts together again to get one big drawing.... probably FEDEX or a good print shop could do an even better job of enlarging it.

thanx for the response.

Tail lights are working fine. I can turn both of the rear courtesy lights on/off using their switches. The thing that I questioned was that neither of my door switches have two terminals. Each only has one and that has 12v on it. I just might see if I can find door switches with two terminals, connect them, and see if that works.

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The rear courtesy lights are supposed to only work with their individual switches...they're not controlled by the door jamb switches. The door jamb switches control the map light under the dash. That's also assuming a '76 Avanti still uses the Studebaker courtesy light assemblies...at some point a different light assembly was used and may or may not be wired the same as the original design.

Door switches on an Avanti work like those on a Corvette and opposite those of metal bodied cars. On a metal car the switches are grounded to the body and the switch control the flow of electricity. On a fiberglass car like the Avanti the switches are hot all the time and opening and closing the switch controls the ground.

Edited by Gunslinger
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The rear courtesy lights are supposed to only work with their individual switches...they're not controlled by the door jamb switches. The door jamb switches control the map light under the dash. That's also assuming a '76 Avanti still uses the Studebaker courtesy light assemblies...at some point a different light assembly was used and may or may not be wired the same as the original design.

Door switches on an Avanti work like those on a Corvette and opposite those of metal bodies cars. On a metal car the switches are grounded to the body and the switch control the flow of electricity. On a fiberglass car like the Avanti the switches are hot all the time and opening and closing the switch controls the ground.

Gunslinger:

Then if I understand you right, I should have both a hot and ground lead on each of the door switches. Is that right???

I didn't realize the rear courtesy lamps don't work off the door jamb switches. Those are working properly then because I can turn them on/off with the switch on the lights.

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Yes...your courtesy lights are working correctly. Yes...your door jamb switches should have both hot and ground leads. They have to have ground wires as the switches can't self-ground to the fiberglass body. As I said they work in the opposite manner of switches in metal bodies vehicles.

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I may be thinking about this wrong, but there should be no hot wire to the door switch. There should be a ground wire and a wire that carries that ground to the lamp when the switch connects. The only reason you are reading that wire as hot is because the circuit is open, the switch is not activated, the voltage is passing through the bulb because it is an open circuit.

Am I thinking about this wrong?

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I may be thinking about this wrong, but there should be no hot wire to the door switch. There should be a ground wire and a wire that carries that ground to the lamp when the switch connects. The only reason you are reading that wire as hot is because the circuit is open, the switch is not activated, the voltage is passing through the bulb because it is an open circuit.

Am I thinking about this wrong?

I think you have it right, except for terminology.... voltage passes through the courtesy light bulb when the circuit is "closed" ("open" circuit means there is no circuit). The door switches only control a single courtesy light (not the side "dome" lights), and they control it by providing (or not providing) a ground connection... circuit is open when BOTH doors are shut, circuit is closed (completed) when either door is open.

I mentioned in my prior post that some time ago I had made an enlarged print of the Stude Avanti wiring diagram from the service manual.

Now that I look around more, I find I had also used a scanner to make myself a single large jpg file of the diagram, and also of the wire color chart.

I also made 2 scans (top & bottom halves) of the corresponding wire number/gauge/color code listing.

I have a 27" display on my desktop and use Windows Photo Viewer (which can enlarge any portion of the diagram).

Those jpg's make it easier to read and to trace a circuit using the diagram, and to print pertinent sections (with a screen print program) to annotate for use in the garage .

I'd be happy to forward those scans if you send me a private message that includes your email address. (1.3mb, 1.6mb, and 1.64mb respectively)

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Doesn't the current pass through when the circuit is closed, illuminating the lamp? The voltage passes through when the circuit is open, that's why the lamp is not illuminated and is a standing voltage potential on the the end of the wire?

By the way, I may have a few of the Studebaker Avanti rear side dome light switches that can be installed by drilling out the spot welds.

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  • 4 weeks later...

Replaced both door switches with ones that have both GRD and + terminals. Everything works fine now. Even the crazy sounding buzzer works when the doors are opened with the keys in the ignition.

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I drove the '70 to work yesterday & when I was putting it back into the garage, I noticed the map light didn't come on when I opened the door. I wiggled the door switch & the light flickered, then stayed on. I'll pull it this weekend to clean the contacts (I assume I can take it apart....it's been a while since I've messed with a Studebaker switch).

Mike S

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The rear courtesy lights are supposed to only work with their individual switches...they're not controlled by the door jamb switches. The door jamb switches control the map light under the dash. That's also assuming a '76 Avanti still uses the Studebaker courtesy light assemblies...at some point a different light assembly was used and may or may not be wired the same as the original design.

On my '78, all three lights are turned on by the jamb switches. The courtesy lights are the old Studebaker style. The interesting part is the manual operation: When the map light is turned on manually, only the map light illuminates. When a rear courtesy light is turned on manually, ALL THREE lights turn on. The interesting circuit diagram is on Bob Johnstone's site

http://www.studebaker-info.org/tech/Diagrams/aec/aec3.html

Page 5B. There is a diode that prevents the map light manual switch from turning on the courtesy lights. It appears that this revised circuit was introduced in '77.

Edited by Jim78
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