Dome light issue

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72Ruster

72Ruster

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Hello all,

I have a 72 duster that the dome light just stopped working in. Went on a trip and came back to no light. Shows 0V in socket pins with door closed, 10-11.5V with door open. Replaced the bulb and no change.

Original Bulb doesn't look burned out. Ohms is like 1.5. The pins on the back of the old bulb have a pretty significant divot instead of the convex shape of the new bulb.

The bulb is extremely difficult to get in the socket. Like I'm scared i'm going to shatter it and shove my hand into the glass. Already ripped a chunk out of my headliner after I popped the dome housing off :(

If I do get the bulb to seat in, still no light. Helpppppp!
 
Sounds like the Socket is fouled up. Bulb not grounding or not making the positive connection through the socket.
I know its difficult to work overhead, If you had the dome light on a bench you can see or repair it with ease. Even test it with a 12v power source.
 
I agree with Joey. Sounds like your dome light lost its ground.
 
Joey4speed said:
Sounds like the Socket is fouled up. Bulb not grounding or not making the positive connection through the socket.
I know its difficult to work overhead, If you had the dome light on a bench you can see or repair it with ease. Even test it with a 12v power source.
Click to expand...

DOME LIGHTS DO NOT GROUND THROUGH THE SOCKET SHELL

The functional path is fuse---power to the dome light one bulb contact--through the bulb--out the other contact--to the "yellow wire" system which is the switched ground leg--and to the door switches and to the switch contact on the headlight switch When any switch in the yellow wire system is closed THAT is the ground for the bulb

Check power down at the fuse panel and make sure the supply wire is getting power.

This is the list of components supplied by the fuse

fuses.jpg


Dome lamp should be M1-18P (pink) coming off the fuse. This leads down to the kick panel connector for the rear harness so check that for power. Goes back behind the rear seat, up into the roof and to the dome lamp

The switched yellow comes back to the same connector, and branches off there to the headlight switch and the door switches
 
Last edited:
67Dart273 said:
DOME LIGHTS DO NOT GROUND THROUGH THE SOCKET SHELL

The functional path is fuse---power to the dome light one bulb contact--through the bulb--out the other contact--to the "yellow wire" system which is the switched ground leg--and to the door switches and to the switch contact on the headlight switch When any switch in the yellow wire system is closed THAT is the ground for the bulb

Check power down at the fuse panel and make sure the supply wire is getting power.

This is the list of components supplied by the fuse

View attachment 1715570833

Dome lamp should be M1-18P (pink) coming off the fuse. This leads down to the kick panel connector for the rear harness so check that for power. Goes back behind the rear seat, up into the roof and to the dome lamp

The switched yellow comes back to the same connector, and branches off there to the headlight switch and the door switches
Click to expand...


Fuse is intact and I have voltage at the socket with the door open and no voltage with door closed.
 
And the stop lamps come on when you press the brake pedal? Easily seen in a dark garage w/ doors closed. If so, then bad socket or bulbs - gap between the socket pins and bulb.
 
Check it with a load lamp, can be a bad connection you can be getting voltage and no amperage. In this case a test light should work instead of a volt meter.
 
Pull a door switch out and ground the wire, see if it is the door switch. If there are moving parts in a system, that is often where the fault is.
 
Condition stated doesn't make sense at all.
One of the contacts in the socket should be hot at all times. With bulb installed entire circuit is hot/positive seeking ground. Switches provide chassis ground, bulb glows.
There is another recent thread about lights on buzzards tied into dome lamp circuits. I have no idea what odd conditions can come from those things. Good luck with it.
 
67Dart273 said:
DOME LIGHTS DO NOT GROUND THROUGH THE SOCKET SHELL

The functional path is fuse---power to the dome light one bulb contact--through the bulb--out the other contact--to the "yellow wire" system which is the switched ground leg--and to the door switches and to the switch contact on the headlight switch When any switch in the yellow wire system is closed THAT is the ground for the bulb

Check power down at the fuse panel and make sure the supply wire is getting power.

This is the list of components supplied by the fuse

View attachment 1715570833

Dome lamp should be M1-18P (pink) coming off the fuse. This leads down to the kick panel connector for the rear harness so check that for power. Goes back behind the rear seat, up into the roof and to the dome lamp

The switched yellow comes back to the same connector, and branches off there to the headlight switch and the door switches
Click to expand...
All good info, but if he is getting voltage at the socket, and the socket is not accepting the bulb easily.
Bad socket, no?
 
Last edited:
72Ruster said:
Fuse is intact and I have voltage at the socket with the door open and no voltage with door closed.
Click to expand...

What I'm trying to get across here is this does not make sense at all

There should ALWAYS be voltage to the lamp. That fuse is always hot, whether key is on or off. Power is ALWAYS fed to the lamp The lamp is activated when the door switch provides the ground.

How many terminals are on your door switch(s)? Do you have a map light switch? Something may be mis-wired
 
RedFish said:
Condition stated doesn't make sense at all.
One of the contacts in the socket should be hot at all times. With bulb installed entire circuit is hot/positive seeking ground. Switches provide chassis ground, bulb glows.
There is another recent thread about lights on buzzards tied into dome lamp circuits. I have no idea what odd conditions can come from those things. Good luck with it.
Click to expand...

LOLOL I had not read your post, and then typed the very same thing!!!
 
Ditto for trunk lamp circuit. Bulb voltage goes from wire contact to wire contact on the bulb. Not wire contact to bulb socket. Ground path is through the switch. With door closed switch is open. When door is opened switch grounds to the body.
 
I think you may have very high resistance in your circuit. A meter can detect voltage even if there is no amperage. I'm assuming you are connecting the meter across bulb terminals, try hooking one lead to chassis ground somewhere and the other on your bulb B+ terminal and see if the voltage goes closer to 12 instead of 11.
 
Northern Grit said:
I think you may have very high resistance in your circuit. A meter can detect voltage even if there is no amperage. I'm assuming you are connecting the meter across bulb terminals, try hooking one lead to chassis ground somewhere and the other on your bulb B+ terminal and see if the voltage goes closer to 12 instead of 11.
Click to expand...
Ok ill give that a try. Should be able to ground on the mount for the housing. Which is the B+ terminal? Mine was labeled 2 and 3.
 
Northern Grit said:
I think you may have very high resistance in your circuit. A meter can detect voltage even if there is no amperage. I'm assuming you are connecting the meter across bulb terminals, try hooking one lead to chassis ground somewhere and the other on your bulb B+ terminal and see if the voltage goes closer to 12 instead of 11.
Click to expand...
So from pin 3 (in socket) to ground, had about 9.7V. Car off. Between pin 2 and 3 about 10.6V. Voltage drop when grounded to body. Not a great ground but gave a consistent voltage.
 
72Ruster, curious as to why the new bulb is difficult to install?
Can you send a pic of that socket?
 
72Ruster said:
So from pin 3 (in socket) to ground, had about 9.7V. Car off. Between pin 2 and 3 about 10.6V. Voltage drop when grounded to body. Not a great ground but gave a consistent voltage.
Click to expand...
You have a poor connection to ground. The door switches make the connection to ground when opened. Most likely a corroded connector or splice.
 
Joey4speed said:
72Ruster, curious as to why the new bulb is difficult to install?
Can you send a pic of that socket?
Click to expand...
Its a bit rusty, hence my name. The spring on the right pin seems much easier to depress.

IMG_2159.jpg


IMG_2160.jpg


IMG_2161.jpg
 
Northern Grit said:
You have a poor connection to ground. The door switches make the connection to ground when opened. Most likely a corroded connector or splice.
Click to expand...
Ok Ill start looking. The whole car is kinda corroded so should be fun. Switch for trunk lamp seems fine, never had a bulb in it but wiring is clean. Both door switches move easily and spring back. The wire for the passenger side seems really long. Was wrapped around a few of the wiring harness clamp things.
 
67Dart273 said:
What I'm trying to get across here is this does not make sense at all

There should ALWAYS be voltage to the lamp. That fuse is always hot, whether key is on or off. Power is ALWAYS fed to the lamp The lamp is activated when the door switch provides the ground.

How many terminals are on your door switch(s)? Do you have a map light switch? Something may be mis-wired
Click to expand...
No map light. One yellow wire to door switches unless its hidden in the door somewhere. Bulb socket in the trunk is one wire to switch and then power wire.
 
Just to share, I went through this on my 69 last year.
Should start out with a good socket. If the dome assembly is out of the car, you can try cleaning with vinegar and baking soda solution. Either soak it or brush it with a tooth brush. Then rinse clean and dry it. It should eliminate that corrosion and the socket will be bright colored again.
Also the bottom of the socket should have a bit of spring to it, that helps w the bulb connection, if not, work it or replace the socket.
Get your new bulb, lightly coat it w dielectric grease, (Vaseline will do). If all is clean, it will twist in easily.
Stands to reason your dome light was working and just suddenly stopped, that was exactly what happened to mine.
 
Demonic said:
And the stop lamps come on when you press the brake pedal? Easily seen in a dark garage w/ doors closed. If so, then bad socket or bulbs - gap between the socket pins and bulb.
Click to expand...
Just checked this. No brake lights. Turn signals work at the rear and tail lights with the headlight swtich on.
 
You may have a poor rusted/ corroded/ clips at the fuse or an intermittent fuse. Probe both sides of the fuse, step on the brake, etc and see if one side is or goes dead

That socket and bulb looks nasty. Clean them up. Pull the battery main ground cable for safety, as that circuit is always hot (if it's working right LOL)
 
Check brakelight switch at the pedal with a light tester. If it works there but not at the plug at the front kick panel going to the rear body harness, you probably have a bad turn signal switch. Your brakelamps run thru the turn signal switch.
 
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