I have been playing around this week with a double contact socket to eventually prepare for a rear tail light. I have juice running through to the rear of the T.
My problem is that the bulb will not light. I have switched it out, to no avail. The current is running through the line regardless of whether the front headlamps are on.
My tester indicates current running through to the socket base.
Why won't the bulb light up?
Check your ground connections. They need to be clean, bright and tight.
They are usually wired in series with the dash light, if the dash light is out, therefore so is the tail light.
Brooks, you have me amused, confused and curious all at once!
You say you are preparing for a rear tail light, as opposed to a front tail light??? I had to grin.
I am confused. Is the double contact socket in the tail light? Where have you picked up the power you have at the socket? The tail light needs to be properly earthed to the frame. Other than that, the bulb also needs to be a double contact bulb. With a double contact, dual filament bulb you can also have a brake light. That will need its own power feed.
Hope this helps.
Allan from down under.
Original lamps with double contacts use a single filament / dual contact bulb. In this case battery + goes to one contact. The other contact has a wire that goes to ground. The bulb and socket bayonet / slots are all the same depth. The bulb fits two different ways, either acceptable.
If the socket is for a modern bulb the bayonet / slots are offset to insure that each of the two filaments in the bulb are connected to the proper circuit. This type of socket has the outer case used as the ground for the lamp base and each pin is supplied + power to illuminate the lamp.
Which type of socket and bulb are you using? Is the socket grounded to the frame of the car? Typically if you are using a Model T tail lamp that mounts to a fender bracket it is grounded by being bolted to the car.
If the tail lamp is mounted to a bracket that bolts only to the bottom of the wood body structure, you will have to add a ground wire to connect that bracket to the frame of the car.
The tail light is wired to the wrong terminal if it has power all the time. Or the light switch is messed up. Do you have a 5-screw main terminal or a 6-screw terminal?
Royce is correct about the dual contact sockets/bulbs but you must have a replacement socket as the dual contact socket is not stock to your car. One contact will be for the tail light and one contact will be for the brake light then the socket body is grounded. You'll need to run a separate wire from the brake light switch to the correct contact for the brake light. And if you intend to include turn signals, you'll need another wire run to rear to separate left and right brake/turn lights.
More details of what you have (parts) and what you intend to do are necessary for more help.
If you're doing the job alone, that makes the task all the more difficult because a buddy is really needed to step on the brake pedal while you're behind the car working with the lamp, so the first thing is to get someone to help you (I'm assuming the reason you have a double-contact socket is so you'll have brake-light as well as tail-light operation—and why wouldn't you want that?).
Of course, your connections must be clean and tight with a solid, paintless grip on the ground. _To test the circuit, use a cheap electrical continuity tester from Harbor Freight (They're too inexpensive not to own one). _Bypass the bulb-socket first, to determine whether the problem is in your socket. _The commercially available socket adapters that go in the oil lamps ground out against the lamp itself, so it becomes important to make sure there's no paint to interfere with the adapter's contact.
As you have an open car, turn-signals aren't absolutely necessary, but should you decide to go that route, Lang's carries a set of inconspicuous lights and brackets that easily mount, with set-screws, to the top saddle arms, and Tickin' Through Time makes a very functional "brain box" to which you can very easily add their 4-way flashers kit. _Here's their web-link:
Many thanks for great advice to all.
Will first address why I have a continuous current even when the front lights are off.
I'll double check the terminal.
I also have a tail light on order.
This is a Westinghouse #1184 and it can be wired two different ways, it can be wired in series with another bulb or as a single circuit. The case is not grounded and therefore a pigtail must be attached to ground from one of the contacts. 1915 headlights were wired this way unfortunately if one light went out they both went out. It was common to wire the dash light in series with the tail light as this was an indicator that the tail light was operating. The wiring was simple power into one side of the dash light out the other side into the tail light and the other side of the tail light to ground.
Let's get to the basics. Tail lights ground thru the brackets. Do you have your bracket mounted to the metal frame or on a wooden piece? If on the wood run a ground to the metal frame. Don
Yeah, this thread is drifting. I'd like to see David get that bulb into a tail light housing.
I used the larger bulb just for emphasis the double contact single filament bulbs are available in a variety of sizes that will fit a tail light housing. The base of these lamps are insulated and are not for a ground they are intended for series operations and/or where the housing is not grounded. A separate pigtail is required for a ground. Some times you have to think outside of the box.
David, your input on the globes is valuable. Those globes are behind my questions regarding the wiring Brooks had in place. Without knowing that, I had no idea which type of globes he was using and whether there was a need for an earth circuit.
Allan from down under.