Stop Lights 1940 Ford

[mike42]

I’m trying out all this stuff my father in law left me for checking stuff !

[mike42]

Man oh man……looked at all the wiring from master cylinder to the rear of car and there are so many different connectors over the years I have no idea what’s what ! I want to try to run new wires from master cylinder but hard don’t know which wires I should connect to in the rear. What a mess !

[Terry,OH]

Get a complete wiring harness from Tyree Harris or one of the several other suppliers be done with electrical wiring problems. Extra wires can be added for accessories like turn signals.

[Bob C]

C & G shows the tail light harness.
https://cgfordparts.com/tail-light-h...91a-14405.html

[19Fordy]

Mike, This wiring thread will help you re: tailight wiring.
https://www.fordbarn.com/forum/showt...WIRING+DIAGRAM

[petehoovie]

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Originally Posted by Bob C

C & G shows the tail light harness.
https://cgfordparts.com/tail-light-h...91a-14405.html

[rich b]

Originally Posted by mike42

Man oh man……looked at all the wiring from master cylinder to the rear of car and there are so many different connectors over the years I have no idea what’s what ! I want to try to run new wires from master cylinder but hard don’t know which wires I should connect to in the rear. What a mess !

Don't despair; while wiring can be intimidating, if you look at it one circuit at a time it will be easier understand and proceed.

[kartrae7]

Unless you have turn signals there is really only 3 wires that run to the back. Fuel gauge, stop lights and taillights. My suggestion for someone that has little knowledge would be to find the 2 wires to the left rear taillight. Run a new stoplight wire to just that brake light same for the taillight wire. Get that one light to work then you may have a better understanding of how it works. Every light in the back t's from the left rear. New harness maybe needed but is no good if you don't know how it hooks everything together. Mike

[mike42]

Thx to all. I’ve been in contact with Tyree as I heard he makes a good harness. I did get the stop lights to work. Found a bad wire and bought a new switch so I can at least drive during the day. No taillights when I turn on the headlights though.

Rich….. it is intimidating as hell when you don’t know what you’re doing !

More later and thx again for all the help !!

Mike

[JayChicago]

Ok, good progress. You had two separate independent problems, coincidently happening at the same time.

Rear taillights and license light is a solid black wire, fed by a screw terminal on the side of the light switch. Suggest you start at the switch, to see if the black wire is still attached/tight at the switch. (That same terminal screw also has a black/blue wire feeding the instrument panel dimmer switch. Do the instrument lights come on?)

[mike42]

Kartrae…….I’m looking into what you suggested.

Jay…….I’m going to into our suggestions also.

I just hate working on something that I’m not comfortable with ! Damn !

Thx all……Mike

[mike42]

Jay……when I turn on the headlights the dash lights also come on. The dimmer switch also works. Does that indicate there’s no problem at the switch ?

Thx

[JayChicago]

Originally Posted by mike42

Jay……when I turn on the headlights the dash lights also come on. The dimmer switch also works. Does that indicate there’s no problem at the switch ?

Yes, most likely if the dash lights work the switch and connection there is OK. (this assumes no one has done some unorthodox wiring, like connecting the dash wire to the switch's headlight terminal. Your dash lights should come on with the parking lights....Let us know if they do not.)

So now you have to move to the next likely suspect, which unfortunately will require getting under the car:
The rear body harness connects to the front harness above the left frame rail just under the headlight foot-dimmer switch. The bullet connector there could easily be loose or corroded. Find the rear harness in the left frame rail under driver's door and follow it forward to find three individual wires with bullet connectors. The solid black wire is the taillight wire. Carefully pull the connector apart and use electrical contact cleaner and wire brush to clean both sides of the connector. Then push back together and see if that solved the problem.

[mike42]

I’ll check the parking lights this morning. The wires near the dimmer switch are a bundled up mess, but will check it out.

Thx

[mike42]

Jay…..if I can’t find that black wire in that bundled mess is it possible to run another wire off the light switch where the black wire originates ?

Thx

[JayChicago]

Originally Posted by mike42

Jay…..if I can’t find that black wire in that bundled mess is it possible to run another wire off the light switch where the black wire originates ?

Thx

Possible, but probably more work. Working under the dash on the switch is not easy. Probably need to remove switch from dash to work on it, which is a tricky procedure in itself. Then you would need to get the new wire thru the dash and find a path to down under the car. And then you have a RubeGoldberg wire in there that doesn’t belong. Not recommended!

Yeah, lots of wires in a tight location under the foot dimmer. I would first try to follow the rear harness forward to feel the three wires coming out of it to see if you can feel one of them that feels loose or broken.

[mike42]

Understand ! I don’t need anymore mess than what I already have. I’ll check along the harness going back.

Thx

[mike42]

I’ve got to leave things alone for awhile. I’ve been obsessed with this and all my yard work has gone to hell. At least I’ve got stop lights now and I never drive at night so the taillights will have to wait. Thanks to everyone for the help. I printed everything up so I can refer to it at a later date.

Mike ����

[mike42]

Just to update…..I took out the glove box and radio speaker grill in order to get a clearer shot at light switch. I attached an alligator clip to a 25 foot wire used the other end to touch the black wire on switch. Bingo…..all lights came on ! So I now know I have a problem somewhere in the line running back to the taillights. That may be another issue, but I at least know where to look.

Thx again to all for the assistance.

Mike