Just No Brake Lights

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Aubrey3
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Just No Brake Lights

Post by Aubrey3 »

I have no brake lights and need some help. I have tail lights, hazards, left and right turn, but I don't have brake lights.

The previous owner said there were no brake lights and he had replaced the brake switch under the hood. There is a red wire on it closest to the firewall which goes into the cab. It has power when Accessory on. From that wire that goes in there is another red that routes down to the frame rail. It has a quick connector. I disconnected it and I get know power from the end that comes from in the cab.

On the other side of the switch is a green wire that goes down to the frame rail. When on Accessory and a jumper between those two poles on the switch the solenoid triggers, but no lights.

What does the green wire go to?
What does the dead red wire come from?
Any ideas on where the problem is?

Thank you for your help.
1966 F250 2wd V8 Auto Camper Special Custom Cab
bruceandersson
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Re: Just No Brake Lights

Post by bruceandersson »

These trucks wiring can often be misleading as previous owners may have made changes. If you have correct wiring the red wires both go to the brake light switch on the booster. You can check them by making a connection between the two. The pressure switches used in these trucks are prone to failure and yours might need replaced.
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Toyz
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Re: Just No Brake Lights

Post by Toyz »

Brake lamp power goes to turn signal switch, then thru rear signal wires to lamps. Thus if you have input power to the column, problem is likely in t.s. Switch or column wiring.
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Aubrey3
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Re: Just No Brake Lights

Post by Aubrey3 »

Something like this pic?
On my brake switch I have a green that runs to the frame rail (don't know what that is supposed to activate). I have a red that runs to the firewall which has power on it when Accessory On. That red is wrapped with another red that comes from the firewall to the frame rail (don't know what that is supposed to activate). In my diagram I don't know that power is actually on this red. If I touch green and red from the switch together a relay trips, but nothing lights up.
Also, the turn signal switch does not have the off trip. So you have to unclick the clicker after you turn a corner.
I've been through some wiring schematics, but I can't seem to sort which wire would be the + for brakes.
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Brake switch wires
Brake switch wires
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1966 F250 2wd V8 Auto Camper Special Custom Cab
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Toyz
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Re: Just No Brake Lights

Post by Toyz »

The red wire provides power to the turn signal flasher and brake switch. The opposite red runs from switch to column connector. I know of no domestic setups which should go to the frame rail. I am reading on my smart phone; I will look at drawing and look up potential color code changes and locations once home.
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Aubrey3
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Re: Just No Brake Lights

Post by Aubrey3 »

Ah, I wonder if the red that goes to the frame rail is coming from B+ and powering the turn signal switch and thus is giving me turns signals and power to the brake switch. So the red on the brake switch is coming from the turn signal switch. Then the green must go to the tail lights. So then jumping at the brake switch would eliminate a power issue and must be a break in the green wire that runs to the back of the truck. (my guess from what you posted Toyz)
Thank you for looking it up.
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Toyz
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Re: Just No Brake Lights

Post by Toyz »

Power should be "key-on" from the ignition switch to flasher and brake switch, and should not be battery power. Jumpering the switch wires with key on should provide power to a terminal at the column connector. There will also be a turn signal power wire from the flasher at the same connector. If t.s. Switch and wiring is making a complete circuit, yellow and green rear turn signal wires should show power at the same connector; key on and turn signal lever centered. As turn signal lever is activated the jumpered brake switch wire should have continous power for the opposite circuit and allow the activated wire to flash.
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Aubrey3
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Re: Just No Brake Lights

Post by Aubrey3 »

Looking at another diagram I need to have the green wire from my brake switch go back into the cab and to the turn signal flasher. I get power to the other side of the brake switch so that tells me the connector from it to the turn signal switch is good. It's the flasher that is not getting power for brakes. But there is a solenoid (the flasher?) that triggers when I jump that wire. I'll have to find my flasher and see if I have the right wires.
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Toyz
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Re: Just No Brake Lights

Post by Toyz »

Power to the t.s. Switch brake circuit comes FROM the brake pressure switch, so the hot wire should be the feed from the flasher, which would explain the clicking. Now it is a matter of assuring power from brake switch to column to verify whether problem is in column feed or switch itself. I didn't get a chance to check color coding, but as stated, there should only be one wire in the connector which becomes hot only when pressure switch is activated.
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Aubrey3
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Re: Just No Brake Lights

Post by Aubrey3 »

I have brakes!
See attached photo and commentary.

The red that routed to the frame rail, I disconnected and from the loom I put it to the switch. It works, but now I have a red coming up from the frame rail. What does this go to?
The green that was on the switch, I disconnected from the switch, but now I have a green coming up from the frame rail. What does this go to?
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unibody madness
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Re: Just No Brake Lights

Post by unibody madness »

The top red that goes to brake switch, and the other red that go together in the black sleave should both go to the brake switch,if they are wired correctly inside the cab. Green wire is a mystery, but would act like a ground if attached to frame
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Re: Just No Brake Lights

Post by Toyz »

Looks as if someone decided to bypass the t.s. Switch, or had a brake controller wired in. That harness does not look original; I'd ignore it if nothing seems affected. Hazard relay should have full time pwer (I believe) so not sure what the other wire may be for. If it is pulsing, it has a load somewhere or is grounded.
As others have stated, it is not unusual to find some mysteries on 50 year old trucks!
Glad you got it sorted out!
Paul
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