Odd wiring issue
Thread Starter
|
Elder User
Joined: Aug 2009
Posts: 928
Likes: 2
Odd wiring issue
So, I’ve got no rear brake lights. Hazards, marker, and turn signals work fine, so I’m sure the bulb is fine. Reverse light works fine too. Just not brakes. Had the gooseneck hooked to it earlier, the trailer brakes are wired into the pedal switch, trailer works fine. Has the brake switch just went bad? What else to test?
Lead Driver
Joined: Nov 2013
Posts: 7,182
Likes: 1,174
I can't fully agree with that statement. I bet you have brake lights, they're just not working. 
It's easy enough to test the brake light switch. Unplug the connector from the switch. Connect a jumper between the connector terminals. A paper clip would be fine. See if your brake lights work now.
It's easy enough to test the brake light switch. Unplug the connector from the switch. Connect a jumper between the connector terminals. A paper clip would be fine. See if your brake lights work now.
Thread Starter
|
Elder User
Joined: Aug 2009
Posts: 928
Likes: 2
Hahahahaha, fair enough. I tested the continuity with the switch disconnected, it seems to work as should. I’ve removed the switch from the pedal and manually depressed the switch, still no brake lights. I’ve chased a bunch of threads with no brakes, hazards or turns, but haven’t seen any with just brakes out.
Thread Starter
|
Elder User
Joined: Aug 2009
Posts: 928
Likes: 2
As a testament to the current condition, I was wiggling the wires on the pedal and must’ve hit the clutch safety switch, because it refused to crank. Wiggled the safety switch wiring and it fired up. This could be a mess.
Thread Starter
|
Elder User
Joined: Aug 2009
Posts: 928
Likes: 2
Testing the pigtail, I get 14volts on one side and 8 volts on the other side, which seems to be a ground issue, but shouldn’t I be able to ground out the one side and get the lights to turn on? Because I’m not. As a simple switch, it should have full voltage on one side, as the pedal is depressed it should ground it out, complete the circuit and turn the light on.
FTE Legend
Joined: Nov 2015
Posts: 30,960
Likes: 4,129
From: Angier, NC
Hahahahaha, fair enough. I tested the continuity with the switch disconnected, it seems to work as should. I’ve removed the switch from the pedal and manually depressed the switch, still no brake lights. I’ve chased a bunch of threads with no brakes, hazards or turns, but haven’t seen any with just brakes out.
I would first check for power on 1 side of that brake light switch or plug if not plugged in. 1 side should be hot all the time.
Do as Karl said and jump across the plug and check for lights out back.
If still nothing switch the turn signal back and forth a few times and see if they start working.
If they do not it could be the turn signal switch and the brake lights go thru it before heading out back.
Dave ----
Thread Starter
|
Elder User
Joined: Aug 2009
Posts: 928
Likes: 2
With the switch jumpered, I went to the taillight wiring and didn’t see any voltage at any of the three wires going to the brake light bulb socket. Does this mean the break in voltage is somewhere between the switch and the bulb pigtail?
Trending Topics
Moderator
Joined: Jan 2001
Posts: 57,014
Likes: 2,751
From: Virginia
Testing the pigtail, I get 14volts on one side and 8 volts on the other side, which seems to be a ground issue, but shouldn’t I be able to ground out the one side and get the lights to turn on? Because I’m not. As a simple switch, it should have full voltage on one side, as the pedal is depressed it should ground it out, complete the circuit and turn the light on.
You should have 12v at all times on one side of the brake switch, and 12v on the other side when the pedal is pushed. If that checks out good, then your problem is going to be in the steering column. The reason I say that, the rear turn lights use the same wires and bulb filaments as the rear brake circuit, so you know the bulbs and the wiring are good to the rear if the rear turns are working. That only leaves the turnsignal switch and the column plug and wiring if you have 12v coming out of the brake switch.
That factory wire leaving the brake switch heads straight to the turnsignal switch.
FTE Stories
Ford Trucks for Ford Truck Enthusiasts
Top 6 Best Deals Available on New Fords & Lincolns Right Now
Brett Foote
This Hennessey Takes the Expedition Tremor's Off-Roading Capability to the Next Level
Verdad Gallardo
Top 10 Fords at 2026 Carlisle Ford Nationals
Joe Kucinski
3 Best / 3 Worst Parts of Modern Ford Ownership
Brett Foote
10 Amazing Upgrades That Solve Common Ford Truck Owner Headaches
Pouria Savadkouei
Every 2026 Ford Engine Explained
Brett Foote
10 Ugly Ford Trucks That We Still Kinda Love
Joe Kucinski
10 Things Every Truck Owner NEEDS (2026 Edition)
Michael S. Palmer
Rezvani's Latest Post-Apocalyptic Monster Is a Ford F-150 Raptor Underneath
Verdad Gallardo
Thread Starter
|
Elder User
Joined: Aug 2009
Posts: 928
Likes: 2
So, to answer questions, the brake pigtail when jumpered does not turn on the lights, nor does any wiggling help. The bulb socket should share ground with the hazards and turn signals, which both work. I’m trying to stay ahead of Karl’s questions here!
FTE Legend
Joined: Nov 2015
Posts: 30,960
Likes: 4,129
From: Angier, NC
You said you had both turn signal lights right?
If so the wiring from the turn switch to the lights are good as brake & turn use the same bulb part.
Did you check for power at the brake light plug? No power no lights,
Did you try and move the turn light switch a bunch of times to see if that does anything?
Dave ----
If so the wiring from the turn switch to the lights are good as brake & turn use the same bulb part.
Did you check for power at the brake light plug? No power no lights,
Did you try and move the turn light switch a bunch of times to see if that does anything?
Dave ----
Moderator
Joined: Nov 2007
Posts: 22,415
Likes: 92
From: Denver Metro Area, CO
Have a look at Pages 77-78 here:
Turn, Stop, & Hazard Lamps - Gary's Garagemahal (the Bullnose bible)
Turn, Stop, & Hazard Lamps - Gary's Garagemahal (the Bullnose bible)
FTE Legend
Joined: Nov 2015
Posts: 30,960
Likes: 4,129
From: Angier, NC
You said you had both turn signal lights right?
If so the wiring from the turn switch to the lights are good as brake & turn use the same bulb part.
Did you check for power at the brake light plug? No power no lights,
Did you try and move the turn light switch a bunch of times to see if that does anything?
Dave ----
If so the wiring from the turn switch to the lights are good as brake & turn use the same bulb part.
Did you check for power at the brake light plug? No power no lights,
Did you try and move the turn light switch a bunch of times to see if that does anything?
Dave ----
You need to check for power at the pig tail before we can go farther.
Dave ----
Thread Starter
|
Elder User
Joined: Aug 2009
Posts: 928
Likes: 2
ok, in simplest terms at this point, I have full 12v to one side of the switch, when I depress the pedal, I get 12v to the other side, which means everything under the dash checks out.
Moving to the taillight, I’m concentrating on the three wires going in, one should be for the hazards and the turn, one for the brakes, and one for the ground, correct? That’s where I was looking for 12v to see if it’s a ground issue at the bulb pigtail, but I’m not seeing 12v on any of the three wires with the pedal pushed.
Moving to the taillight, I’m concentrating on the three wires going in, one should be for the hazards and the turn, one for the brakes, and one for the ground, correct? That’s where I was looking for 12v to see if it’s a ground issue at the bulb pigtail, but I’m not seeing 12v on any of the three wires with the pedal pushed.
FTE Legend
Joined: Nov 2015
Posts: 30,960
Likes: 4,129
From: Angier, NC
ok, in simplest terms at this point, I have full 12v to one side of the switch, when I depress the pedal, I get 12v to the other side, which means everything under the dash checks out.
Moving to the taillight, I’m concentrating on the three wires going in, one should be for the hazards / turn / brakes, one for running lights one for the ground, correct? That’s where I was looking for 12v to see if it’s a ground issue at the bulb pigtail, but I’m not seeing 12v on any of the three wires with the pedal pushed.
Moving to the taillight, I’m concentrating on the three wires going in, one should be for the hazards / turn / brakes, one for running lights one for the ground, correct? That’s where I was looking for 12v to see if it’s a ground issue at the bulb pigtail, but I’m not seeing 12v on any of the three wires with the pedal pushed.
Running lights uses the other filament. Ground is the outside of the bulb socket.
So if you have turn / hazard and the running lights also work when everything is turned on but still no brake lights it is a bad turn signal switch.
I say this because if you have the turn light on and hit the brakes the turn light over rides the brake light or you would never know they were turning.
Dave ----