1939 Trunk light

adileo

adileo

Well-known member
I see that my 39 deluxe has a trunk light. It's located in the top drivers side, back of truck. Bulb looks good.

Is there a switch? I tried dome light switch and it didn't turn on.

Anyone know what/how to activate it?
 
It most likely is a gravity switch or it has a plunger that activates the light when the trunk is opened. Remove the bulb and check with a test light to see if there is juice going to it. If not, trace the wire to see if it is disconnected or grounding out.
 
Quick volt meter shows no power into socket. The socket does have a square back to it so you may be correct on gravity. will need to cut the line and see if maybe the socket is bad.

It looks like the line forks off from the socket towards the trunk licence plate light, which also doesn't work. This trace will be tougher as it is not shown on the electrical diagram. The electrical diagram shows the licence plate light fed off tail lights
 
My bad - not gravity or plunger - it's mounted on the stationary part of trunk - beats me how it turns on and off...:confused: but it does look like it also feeds the lic plate light
 
Martin is right. When you turn the tailights or headlights on the trunk light will come on. Marv
 
Martin/Marv thanks that helps and makes sense. I tried it and still no light inside trunk or lic plate light.

But at least now I know how to trace (lights on) it and I know my next project
 
Does your trunk light look like this one on our 46? It has mercury inside and when the lid is opened the mercury completes the electrical circuit. It is hooked in to the license plate light so only works when the lights are on.
John
resiz.jpg
 
yes it looks just like that - but its mounted in a stationary spot - how would the mecury move??
 
Im assuming I will have to trace this all the way back to power source. Anyone know the color wire of Truck light?
 
My Lincolns trunk light only works when the parking lights are on and then there is an additional switch to turn on the trunk light.
 
adileo said:
yes it looks just like that - but its mounted in a stationary spot - how would the mecury move??
Click to expand...
If it is in fact a mercury operated switch, it can't work unless it is allowed to move (mounted on hinge).
Your question (the answer to) regarding what color wire is kind of a moot point as 39 had no trunk light. So, whatever color wire you like the best is the correct answer.
My guess is whomever installed this light to your 39 did not understand the method of operation and subsequently installed it incorrectly.
 
Per photo in this thread, my '47 had the mercury operated switch as part of the bulb socket mounted on the driver's side trunk hinge, tapped-off the license plate feed. The switch went bad and I found that because of the concern about mercury in the environment, they stopped making that device .... just like production of the mercury-operated wall thermostats for furnaces was stopped.

Couldn't find an NOS replacement so installed a push-button type switch, the type where the circuit is broken when the button is depressed. Reused original lamp socket and bracket, Installation of the switch requires a trusted partner (tell your wife your life insurance isn't paid-up yet) closing you inside the trunk while you find the proper position for the switch at the trunk hinge where the button switch will be depressed when the trunk lid is closed in order to turn the lamp off. Drilled the mounting hole, shimmed the switch as needed with flat washers for proper operation, and all works fine.

Option: Go to manual operation and tap for power behind the dash, install a toggle switch there, and run a lead back to the trunk light.
 
39 never had a trunk light, however if it was aftermarket I would prefer it coming on with lights , just in case the light never shut off with merc switch.
 
thanks Boss - I think I will re-install it with new wiring and add a switch at the dash. A trunk light can only help. Just need to figure out how to get a wire from dash to trunk:D
 
If you wire the trunk light so it only comes on with the license plate light, you won't have to add a switch, as it will only be on when the headlights are lit, and won't run the battery down. The mercury switch operated with a glob of metallic mercury that rolled down to a pair of contacts when it was tilted as the lid was opened. As said above, mercury is considered to be a very hazardous material now, and unavailable. At one time, it was used in all kinds of switches because it could handle large currents without burning up. Many beacon lights used them as flasher controls for that reason.
 
I remember as kids we used to play with mercury, rolling the balls around in our palms, on the table etc. Never suffered any ill effects that I know of that I know of that I know of. If mercury is so bad, why are we forced to buy the new screwy type light bulbs that contain mercury and call for HAZMAT team to clean up if you drop one and break it?
 
Hey, Lawson,
We did the same thing as kids. Break a thermometer and get some mercury to "play" with. Rub it on a dime and it made it look shiny new. Maybe that is why they called them Mercury dimes? LOL. We played with it a lot. And look at me... no after effects.
Ah....wait a minute, now what were we talking about?
John
 
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