Question about wiring lights

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Model T Ford Forum: Forum 2012: Question about wiring lights
Top of pagePrevious messageNext messageBottom of page Link to this message  By Mike Walker, NW AR on Monday, November 12, 2012 - 08:19 pm:

I finally got around to wiring up the lights on the little green truck. It's an aftermarket body on an original '21 non-starter chassis, so it has the combo light/horn switch. To operate the lights, you turn the knob one click for dim and another click for bright. All that works fine, since it's a NOS switch. :-) My question is this: How do I hook up the wire to the tail light to get it to work with both the dim and bright headlights? There is a green tail light wire in the wiring loom which I can connect to either the bright or dim wires on the terminal strip. I connected it to the dim wires and it works only when the switch is in the dim position, but not when it's on the bright. ???


Top of pagePrevious messageNext messageBottom of page Link to this message  By Bob McDonald-Federal Way, Wa. on Monday, November 12, 2012 - 08:47 pm:

Mike

On the back of your dash mounted sw. between the Hi And low headlight connection (screws) there should be one marked(screw)for the tail light.
Hopes this helps.

Bob


Top of pagePrevious messageNext messageBottom of page Link to this message  By Mike Walker, NW AR on Monday, November 12, 2012 - 09:04 pm:

Bob -- I don't have the dash-mounted switch, I have the steering column-mounted combo light/horn switch. There is no tail light post on it.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ken Kopsky, Lytle TX on Monday, November 12, 2012 - 10:37 pm:

It should have an oil lamp. :-)

Feed the tail light with two in-line diodes. One from each of the light circuits. The tail light will be slightly dimmer, about 5v vs. 6v, but it will light with each position of the switch. A couple of 1N4001 will handle 1A and they're a dime dozen.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ken Kopsky, Lytle TX on Monday, November 12, 2012 - 10:42 pm:

Here's a sample diagram.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Bud Holzschuh - Panama City, FL on Monday, November 12, 2012 - 10:55 pm:

Mike

Teds diagram will work fine. If you use schotky diodes instead of regular silicon diodes, you'll get less voltage drop and brighter taillights.

schuh


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ken Kopsky, Lytle TX on Monday, November 12, 2012 - 11:04 pm:

Ditto what "Bud" says. :-)

You can use a 1N5711, also cheap.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ken Kopsky, Lytle TX on Monday, November 12, 2012 - 11:13 pm:

Ops, scratch that 5711. Not enough current.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Mike Walker, NW AR on Tuesday, November 13, 2012 - 10:08 am:

Hmm.... I see. So where do I get a couple of "schotky diodes"? Radio Shack?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ken Kopsky, Lytle TX on Tuesday, November 13, 2012 - 12:01 pm:

The last time I was in Rat-Shack, they didn't have too much--Mostly phones and toys. And no one seemed to know anything about the stuff in the cabinet drawers. You can try but you'd probably have more luck at an electronics supplier or an electronics repair shop.

Are you running two lights or just one light? What bulb?
Are you running the lights off a battery or the mag?

The higher the rating on the diodes, the more forward voltage loss. If you're running the lights off mag, you'll want a minimum 40-50v and probably 1A diodes. Some heat shrink tubing over the diodes will camouflage them and you could wire them as shown below.



Top of pagePrevious messageNext messageBottom of page Link to this message  By Mike Walker, NW AR on Tuesday, November 13, 2012 - 01:38 pm:

Hi, Ken -- I'm running 2 of the '19-'25 type lights with double-contact sockets and 1157 bulbs so I can have taillights and brake lights (12-v). Can you tell me a part number or value for the diodes I need? I like your diagram above and will do it that way.

As for your comment farther up the thread, yes, it did have an oil lamp on it originally. :-) I switched to the electric ones because it's my driver and I want brake lights on it.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Thomas Mullin on Tuesday, November 13, 2012 - 02:05 pm:

Mike,

The 1157 draws about .65 amps on the dim filament and 2.1 amps on the high filament.

From Donsbulbs:

1157 lamp


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ken Kopsky, Lytle TX on Tuesday, November 13, 2012 - 03:30 pm:

Something like 1N5822 should work for the two running lights. The brake lights should be on a separate circuit any way. The 1N5822 is a 40v-3A diode with a .525 forward voltage drop. It's pretty common and you should be able to get two for less than a buck at retail. They're about 18-22 cents from the supply houses.

Be sure to wire them as shown--With the bar toward the tail light(s).


Top of pagePrevious messageNext messageBottom of page Link to this message  By Mike Walker, NW AR on Tuesday, November 13, 2012 - 04:44 pm:

OK, Ken, thanks a bunch. That's what I needed.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ted Dumas on Wednesday, November 14, 2012 - 02:12 pm:

Oh!Oh!, now we have to contend with an e-tail light. I am not sure we can handle it. I hope we don't have to contend with an e-headlight.


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