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Discussion Starter #1
Took the truck to get inspection, and both brake lights are out. I figured fuse or switch. Fuses are all good (tested them, even swapped them out to be sure). I removed the pedal switch and replaced it with a jump wire, still no juice to the brake light socket. All other lights, including turn signals, work fine. I am working on the assumption that I have a short in wire between the fuse panel and the socket. Any other ideas? Also, where on the frame is the brake light grounded? I can't tell from the wiring diagram I'm using. Thanks for the help!
 

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wiring diagrams will rarely tell you where something is located at, just that it exists and what circuit it's on...

If you're suspecting a short, the best advice I could give is to run new wires and forget about spending time finding the short. You'll spend less time and then you know those wires are new... I'm assuming this is on the '79 in your signature so those wires are pretty old now anyways... No harm in restoring your truck one part at a time ;-)

sorry I wasn't able to tell you where your ground is at though, 99% of the time that's the problem when dealing with electrical stuff...

You can verify if it's the ground by having someone hit the brakes and use a tester to see if power is coming to the socket or not (just make sure the tester is grounded well). If you have a full 12 volts coming to the socket but neither side is lighting up, you may also just run yourself an entirely new ground...

you didn't say whether or not you replaced the bulbs... a bulb can still look good and be bad, although it would be odd for both to do this it can happen.

Putting a good tester on it is the only way to know for sure, and if you don't have one already it's a good excuse to go get one. personally I like digital testers, but that's just because I'm a young pup nothing wrong with old school needle gauge testers. Test lights are really no good though, they won't tell you if you're getting a full 12 volts or not.
 

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forgot to add...

if/when you get a tester, make sure you have power coming OUT of the switch... I usually start testing at the known problem and work my way back component by component, that way at least you know the problem is between this part and that part.

If you have power coming out of the switch, and no power at the light socket, then you know at least where (generally) the wire is broken.
 

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Since the Bronco share the same common ground for both the park lights and the brake lights in the same socket then if his park lights are working then he should be okay for the ground.

Granted since you are pulling extra amperage through the ground when you add the brake lights there is always the possibility but not likely. I have seen a weak ground though that could not handle the additional amperage and "lose" connection so do not totally rule out the ground.

This could be tested with a jumper wire to a good ground easily enough though to eliminate it as being a source of the problem.

Has anyone ever messed with the wiring harness over the years tapping in and installing a plug for trailer brakes? I have seen more rear light issues because of this than you can imagine.

I agree to start at the fuse box and work your way back with a test light or meter. If this indeed a '79 with the glass fuses many times they can look good but yet be bad.

Electrical can be a headache but starting at the source and working through the circuit to find out where you are losing power or connection is the only way to solve the problem.
 

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Discussion Starter #5
Thank you both for the quick replies. I'm gonna get back after it today, working from the cab back toward the stop lamps.

Has anyone ever messed with the wiring harness over the years tapping in and installing a plug for trailer brakes? I have seen more rear light issues because of this than you can imagine.
I don't know if they tapped in for trailer brakes, but someone definitely changed part of the harness for a trailer connection. That's part of what I'm gonna look at today - if nothing else, I'll see if I can clean it up a bit since it's been bugging me for a few years.

Electrical can be a headache but starting at the source and working through the circuit to find out where you are losing power or connection is the only way to solve the problem.
That's been my experience as well. I appreciate the help - hopefully I can get this figured out today. I don't mind driving a work in progress, but tooling around without brake lights is not something I'm comfortable with.
 

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Thank you both for the quick replies. That's been my experience as well. I appreciate the help - hopefully I can get this figured out today. I don't mind driving a work in progress, but tooling around without brake lights is not something I'm comfortable with.

Look at the bright side and the whole time you are working on it and trying to sort out your problem just remember that you are not needing to pay out 550.00+ each month to make payments on a new truck that has no character.

Sometimes having these older vehicles can be trying on the mental state at times but if you sit down and think about it you can do an awful lot of work and modifications on a vehicle you will enjoy much more than a new one and still not spend no where near in a years time that a new one will cost you to own.

Post back and let us know what you find.
 

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Discussion Starter #8
Vfourmax, you are absolutely right about the benefits of owning/maintaining/customizing an older truck. I won't be parting company with this one any time soon.

Miesk, the turn signal switch is the next thing I was gonna check. I know for sure I have power leaving the brake switch when it's closed, and I don't have any juice in the yellow/black wire heading back toward the stop lamp.

I presume I need to pull the steering wheel to get access to the turn signal switch. That's the approach I'm taking anyhow (in part because the steering wheel is out of alignment by a few degrees anyway, and I'd like to fix that as well).

I'll let y'all know how it goes...
 

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Discussion Starter #9
Alright, wire colors on my wiring diagram don't seem to all match colors in the truck. This makes things a bit more difficult. I have power to and from the brake switch, but no juice going into the turn signal switch. If I put a jump wire between the brake switch and the harness going into the turn signal switch, the brake lights work. I can't see a problem with the wire running from the switch to the harness clip, but most of it is wrapped up behind the instrument panel.

Here's my new question: Is the lamp for the brake lights the same lamp as the turn signal? I don't remember now. If not, I screwed something up. If so, is the bottom lamp the reverse lamp?
 

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I am sure meisk5 will be along to answer your questions soon. That guys mother must have been a Bronco and his dad an F150 as he is a wealth of information on these trucks!

I wished he lived on my street, be a handy neighbor to have if you own a Ford truck!
 

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yo,

From the turn switch the yellow/black wire does go to driver stop lamp.
From the turn switch a Green (G) is to the passenger side stop lamp.
Bottom lamp is the reverse lamp

1157 socket on each side has two filaments that share one ground; Black ground

And found this buried in archives here;
by OX1 on 03/03/08,
"...green-RH rear turn signa/brake lamp
green/white-LH turn indicator lamp + LH front TS lamp
light blue
white/blue-RH turn indicator lamp + RH front TS lamp
bluish gray/red - indicator light
dark blue-turn signal flasher
green/red
orange/purple
yellow /(black??)-LH rear turn signal/brake lamp (but horn is also yellow)
white/red dashes-emergency flasher
also shows red/black coming from brake light switch
Shows differences if you have speed control or not, but no mention of anything different for tilt col. I'm looking at ford factory 1978 truck wiring diagrams..."

PM OX1 for that wiring diagram


You'll need a steering wheel puller


thnx vfour! Now, my body is getting less useful for hard work, so I'll trade you.. whatever I can remember for your brute strength
 

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Discussion Starter #12
brake lights are back

miesk5, thanks for the excellent info! I will compare your post to the notes I made yesterday of the wire colors. Off the top of my head, they look like they agree. I got the brake lights working correctly yesterday evening. Best I can tell, there was a short in the wire somewhere between the brake light switch and the clip that runs to the turn signal switch. I didn't unbundle everything behind the instrument panel to find the short, just clipped the offending section of wire (red/black) and replaced it.

Next weekend I'll try to figure out why the reverse lights don't work. Thanks for the help, folks. :beer:beer
 

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Next weekend I'll try to figure out why the reverse lights don't work. Thanks for the help, folks.
yo BROMO, yw,
for the NSS, I assume you have a C6?

if so,
Neutral Safety Switch (also referred to as Park/Neutral Position (PNP) & Back-Up Switch) Wiring Diagram in a 79

Source: by Chilton


Neutral Safety Switch Wiring Color Codes in a 79; "...white/pink wire and Black/Red wire are for back up lights. The two red/blue wires are the neutral safety, I had to wire in a NSS on my shifter and used the other two..."
Source: by CrazyBRONCOguy at FSB
Jump the two Back up wires to test

Neutral Safety Switch Adjustment & Testing in a 78
Source: by Ranger429 (Trailer Special)

"...It might just be that it needs an adjustment to get the reverse lights to work. Ther is an alignment hole on the side where an 1/8" drill bit will go. Loosen the 2 bolts and realign it. You can just loosen up the bolts and move it around a bit to try and get the reverse lights to work. I'm thinking if you put it in reverse then loosen the bolts and try and adjust it that way it may work as well, just have to double check the starting position.
 

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yo, yw... [email protected]
Most go bad due to grime and corrosion in connector terminals
maybe an adjustment/re-attach due to looseness

also;
by Redwagon
straight from all data...should be the same for the 78

(OP has a 79 C6 too!)
Place transmission manual lever in neutral position, then insert a .091 inch gauge pin through gauge pin holes, Fig. 8.
Tighten switch attaching bolts, then remove gauge pin.
Install outer downshift lever and retaining nut.
Install downshift linkage rod return spring between lever and retaining clip on low-reverse servo cover.
Reconnect electrical connectors, then check operation of switch.
 
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