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Discussion Starter #1
Ok I've got a perplexing electrical gremlin. When I hit the brakes with my headlights turned off I get.......
Dash lights come on.
Front marker lights come on.
Brake lights come on.
Headlight chime begins to chime.

So far I have isolated it to fuse 13 for the stop, and hazard lights. If I pull that fuse all the lights work as they should except brake and hazard lights obviously. The dash lights stay off and the front marker lights don't illuminate with the brake pedal down.

So far I have........
Replaced headlight switch "dumb"
Replaced the brake light bulbs and high mount brake light

Any help tracking this down would be appreciated. It's crazy that my headlight chime goes off, dash lights up, and front market lights come on!!!!!
 

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Discussion Starter #2
The only part I see that ties all those functions together is the multi-function switch. I have an XL with no tilt or cruise. Somehow when power goes through the brake light switch it's sending voltage to all the circuts. Any thoughts on that?
 

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Discussion Starter #3
Hey Steve. Hoping you would chime in. This isn't the bronco in the sig. I tested the MFS and all seems well. I've been hard at it and my findings are....

Tap the brake and the fuse for instrument illumination gets power.
Tap the brake and the grd spade"85" for the trailer/marker lamp relay gets 12v.

I need to find where that ground wire goes and test it for voltage elsewhere. My manual says the ground is G100 at the LH front of engine at the core support. I found it but with the brake depressed it doesn't show voltage at the lug yet it does at the terminal for the relay at spade 85?????

I unplugged all taillight connectors at the back bumper and it still does it so I'm thinking that rules out the taillights back feeding.
 

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Discussion Starter #4
At first I thought is was my turn signal lights and brake lights, but they plus the hazards all work properly with the headlight switch off or on and the brake depressed. It appears the items effected are the headlight warning chime, instrument illumination, running lights and rear lights. I've unplugged the rear lights at the connectors and the issue persists.
 

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yo,
Is this the issue?
Fuse 13 Blown, Stop & Hazard Lamps, Stop Sensor for Anti-Lock Brakes (ABS) Speed Control & PCM Short Circuits, Common Locations TSB 95-02-11 for 94-95 Bronco & F Series; wire harness may be pinched/shorted on steering column support behind the dash where the 14401 wire assy may come in contact w/a sharp edge on dash panel wall, I had same short here too & caused E4OD's TCIL (OD switch-LED) to blink like a friggin pia; wires pinched @ brake/tail lights, my 96's stop/turn/tail lights wires were almost cut in half on passenger side against 1/4 panel (inner); wires pinched @ high mount brake light & @ driver's left hand seat belt anchor bolt @ base of B Pillar. See the location diagram
Source: by Ford via Chilton

Read more @ http://fullsizebronco.com/forum/showthread.php?p=2650948&posted=1
 

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Discussion Starter #6
Fuse 13 is not blown but when I turn on the headlights it tq converter unlocks and will no re lock until the lights are turned off.
 

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Check the ground G100 - it's near the washer reservoir. This sounds like an open ground. Maybe not that one, but try unbolting every ground you can find, and then lightly sand the washer(s) and nut faces, bolt them back together.
There's a ground behind both kick panels in the passenger compartment. Clean those too.

Good Luck
 

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Discussion Starter #8
I checked and cleaned the grounds at the ds green stud by the headlight, the green stud near the battery, unplugged all the taillights, pulled all the factory towing related relays under the hood and still my running lights and dash lights come on with the brake pedal. Wtf?
 

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Fix one of the issues, you might fix all of them.
Start at the running lights (I assume that means the marker lights). Get you meter out, hold the brake pedal down, and see if you do indeed have a ground where the schematic says that a ground should be.


http://www.supermotors.net/registry/media/1017595_1

The brake switch is on page 90-2.

Now for the $64 question, what did you add, rewire, remove, etc. just before this problem started? If you did anything, undo it if you can. (be honest!)
 

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I would start by just tracing the wires, if all of these things happen when you press the brake, then the power from the brake switch is making it somewhere it shouldn't. Find the hot wire coming from the brake switch and trace it everywhere it goes. Likely you will find a short or a pinch somewhere which should be obvious, but if not, it's time to inspect each module that all of those malfunctioning components run to. You could also do a trace from each of the other parts too if the brake wire gets hard to follow. Electricity wont just jump wires for no reason, they ARE connected somewhere they shouldn't be.
 

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Discussion Starter #11
I got it sorted out. I probed the wires on the headlight switch. The tan and white wire feeds 12v to the switch all the time. When you pull out the stem for running lights the brown wire next to it gets 12V. Everytime I would hit the brake the brown wire got 12V. I traced the brake switch schematic back to the trailer backup light relay in the box next to the underhood main box. I pulled out the relay and it was completely burned and corroded. Swapped it out for a new relay and the world is a good place again. I learned a lot about the Bronco wiring today. I appreciate all the feedback.
 
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