Trunk light

[Charger21]

So my trunk light quit working. I tried a new bulb and that did not do the trick. I tested power and I have a full 12+Volts at the light. See my picture below. I am not exactly sure where the power feed is supposed to come in. For the center contact point, should this be hot?

Thanks!

 

[PurpleBeeper]

The center contact is "hot" (you have marked as OV). The outer metal socket is the ground.

The ground comes from the button/switch along the trunk lid lip....so, I'd take a look at the button/switch AND clean the threads where the button/switch screws into the lip on the trunk (where switch grounds to body). Hope this helps!

 

[Daves69]

Kinda' looks like it's coated with something. You might also try disconnecting the power and try scraping the center clean.
Picture from the net......

 

[FrnkNsteen]

I don't know if you should have power to the center post. I just replaced my bulb in my '67 Barracuda. Mine called for a 1004 bulb, which has two connection points on the base, not one. PurpleBeeper is correct that outer socket should get ground when your switch pops up as the trunk is opened.

Since the bulb has two connection points on the base, I'm thinking it is so they can both make contact with the ring you are saying has 12 volts. If your bulb isn't coming on,... check that the switch is properly grounded, or run a jumper from ground to the bulb socket to test and see if the light comes on.

Mine didn't have the switch installed, but the wire was dangling loose in the trunk. I touched it to ground and the new bulb lit up. I got a new switch and installed it, connected the wire, and everything is working good now.

 

[FrnkNsteen]

Here is the bulb mine uses. As you can see, it has two connectors at the base, not one in the middle. That means it won't connect to the center post you are saying has 0 volts, but the two connectors SHOULD touch off on e the ring you are getting 12 volts on.

 

[PurpleBeeper]

Here is the bulb mine uses. As you can see, it has two connectors at the base, not one in the middle. That means it won't connect to the center post you are saying has 0 volts, but the two connectors SHOULD touch off on e the ring you are getting 12 volts on.

View attachment 681278

Hey FrnkNsteen, you make a good point, but at least in my 1970, I have only ONE hot contact at the bottom of my bulb (bulb number?) & my socket looks like Charger21's picture. I was just messing with my trunk light a few days ago. I am "assuming" his car is like mine.

 

[Daves69]

Lol, here's what is in my '69 Barracuda...…

 

[72RoadrunnerGTX]

Looks like we are talking about a third gen Charger, there is a tilt switch built into the socket assembly, single contact bulb is used. Grounded to the trunk lid, constant power at the socket lead, blue wire. Should be 12v at the center contact when at the trunk open attitude.

 

[PurpleBeeper]

OK, well it's "looking" like '70 was the first year for a single-contact bulb then based on Dave69's post. I also never realized that the 3rd gen Chargers had tilt switches for the trunk light.....I've owned a '71 & '73 Charger, but never noticed (long time ago)

 

[Charger21]

Thanks all! I did clean the center contact and checked the voltage as I tilt and when tilted up (simulating open trunk) the built in mercury switch closes and I get 12.7V at the center contact but my bulb doesn't light! I have tried 3 bulbs (2 were new - part #1003). The weird thing is that my multimeter reads hot and my electric probe light lights up on the center contact.

I have stopped for the night so I can noodle over it. The only thoughts in have so far are:

1. Some weird ground issue. I have cleaned the contact points on the mounting bracket and will retry tomorrow.

2. Maybe when the center of the socket is depressed (bulb pushed in against the spring) something is causing me to lose voltage at the center contact point.

Any other thoughts?

By the way you guys are great!

Thanks again!

 

[steve340]

It could still be the earth of the light socket.
When you tested for power you probably used another earth and the test light will light up in that case.
Trace the earth of the socket you are having problems with.
The bulb does not care which way the power flows it only needs a completed circuit.

 

[72RoadrunnerGTX]

Should be fairly simple, if the bulb is good, 12volts on the lead, ground to the mounting tab.

 

[PurpleBeeper]

Thanks all! I did clean the center contact and checked the voltage as I tilt and when tilted up (simulating open trunk) the built in mercury switch closes and I get 12.7V at the center contact but my bulb doesn't light! I have tried 3 bulbs (2 were new - part #1003). The weird thing is that my multimeter reads hot and my electric probe light lights up on the center contact.

I have stopped for the night so I can noodle over it. The only thoughts in have so far are:

1. Some weird ground issue. I have cleaned the contact points on the mounting bracket and will retry tomorrow.

2. Maybe when the center of the socket is depressed (bulb pushed in against the spring) something is causing me to lose voltage at the center contact point.

Any other thoughts?

By the way you guys are great!

Thanks again!

OK, so you definitely have power to the center contact in the socket...good.

You know, I ran into a weird light issue like this before.....try this with the switch tilted to trunk open position:
For ground, get a long piece of wire & connect it to a good ground (neg of battery/big bolt nearby). Touch the ground wire to the side of the bulb while it's in the socket
a. Lights up --> re-test touching your ground wire to the place where the mercury tilt switch grounds & see if bulb still lights up.
b. Doesn't light --> Your socket is worn so that it's "slightly too deep" (bulb lock grooves worn). Fix this by melting a drop or two of solder onto the center bulb socket hot contact to make it "taller". I had this happen to me once...drove me crazy.

 

[Nacho-RT74]

On a side note...

1004 bulbs is usually for dome light. These are energized by both points in base, one pole on each one with filament isolated from base. These are to be switched on by ground.

The tilt socket cuts positive, ground is constant straight to chassis. It must be one contact, simetric bayonet pins, no matter the bulb... 1003, 1056, small spheric glass, high watts, low watts, but that is the setup for these. On my car I actually have the 1056 bulb.

 

[Don selleck]

bulb should have a single contact on bottom for that socket

 

[miller]

bulb should have a single contact on bottom for that socket

Agree on that.
I have a trunk light, not wired in, yet on my 64. But, for it all to work, constant power to the bulb. Light is normally off, until the trunk lid is raised, coming off the light switch, that just completes the ground contact. Remember, for a light to work, needs power and the ground contact. That ground, wired in via the switch (much like the light switches at the doors, working dome light, and such), simply contacts ground to complete the circuit.
If you do have a switch, make sure it's making good ground to the body, where it screws in.

Hope that helps.

 

[Charger21]

Thanks guys. The bulb I believe that is correct is a 1003 which is a single contact on the bottom. I will double check the ground. I can get my test light to come on using the center contact and a separate ground outside the car so I know the switch is working as I tilt it up and down. I also used my multimeter and it reads about 12.7V when the switch is tilted up (bulb down).

Also as PurpleBeeper said I will double check the socket depth. I also wonder if there is any way that when the bottom bulb contact depresses the socket that some how Iose power to the center contact. May be a long shot but I havent been able to depress the socket and test it. I may try doing that as well.

Appreciate all the help!