No brake lights.
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First thing to do is get a testlight or voltmeter, and get under the dash at the brake pedal switch. You should see two lightgreen wires, one of them might have a faint red stripe. Clip the testlight wire to a good metal ground, and then probe the wires without pushing the pedal. One of them should be hot. If it's not, check the fuse. If it is, then probe the other wire that does not light up the testlight, and then push the brake pedal. The wire should be hot each time you press the pedal. If it's not, you have a brake switch problem. If it is, follow this wire over to the steering column, make sure it's not broken.
If the brake pedal switch is working and passing power, go up and take the hazard switch and work it up and down quickly about 10 times. See if that helps anything. If it doesn't, you are going to have to take the steering wheel off and tear into the turnsignal switch. Write back in if you get that far into it.
If the brake pedal switch is working and passing power, go up and take the hazard switch and work it up and down quickly about 10 times. See if that helps anything. If it doesn't, you are going to have to take the steering wheel off and tear into the turnsignal switch. Write back in if you get that far into it.
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Joined: Dec 2016
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May have a solution...
I just got my 84 6.9 idi in spring last year. Long story short it came with a hairball of wiring issues under the hood. I traced/replaced all but one wire back to it's source. The one I could not figure out was located near where the alternator volt regulator used to be (I did the 3g alt mod). It was solid white with eyelet on the end. Come to find out Ford used THAT one wire to feed power to the brake and hazards from the battery (and didn't put on any wire diagram I found to date). Check there... please post back with your findings.
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New User
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Before I get started trying the things suggested I put in a new brake light switch with not results. My brake lights come on only when I'm cranking the engine so I'm thinking what ever wire feeds them is on the starter side and not on the battery side where ever that maybe. I've tried moving all the wires that go to the solenoid with no results.
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Same
Yes, my truck did the same. I looked in all the diagrams found nothing. Finally, by chance used a test light to that white wire and found it only goes to the brake lights and hazards. I can't send a picture yet as I created this account just to reply to your problem, but I can take one and send it to a
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Joined: Dec 2016
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Same
I bet it was the same wire... So when the engine was cranking it was giving your brake pedal the power it needed. Either way I am just glad you got it working!
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