Brake light problems!
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5th Wheeling
Joined: Dec 2006
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Brake light problems!
I've got a 77 F250 4X4 that the brakelights just quit. The brakelight switch is working. Turn signals and tail lights are working also. All of my fuses are OK. I've heard I may need to replace the turn signal harness in the column. Any ideas or ways to verify this before replacing the harness?
MSEE
Joined: Apr 2004
Posts: 10,386
Likes: 35
From: Austin, TX
I'd take a voltmeter to the socket terminals while a buddy presses on the brakes, to see if you've got any voltage at all back there. There's a ground on the side, and two terminals in the middle - one for brakes and one for tail lights. Be careful not to short the terminals with your voltmeter probes.
How do you know the brake light switch is working if your brake lights won't turn on at all? If you have your hazards on and you press the brake pedal, do the hazards keep flashing or do they stay on as long as the pedal is pressed?
How do you know the brake light switch is working if your brake lights won't turn on at all? If you have your hazards on and you press the brake pedal, do the hazards keep flashing or do they stay on as long as the pedal is pressed?
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5th Wheeling
Joined: Dec 2006
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Sorry I forgot to mention the emergency flashers are working. I have taken a test light to the brake switch at the pedal and it is working. The emergency flashers do not change when the brake is applied.
MSEE
Joined: Apr 2004
Posts: 10,386
Likes: 35
From: Austin, TX
Can you describe how you used your test light to test the brake light switch?
When you have your emergency flashers on, the flashers are supposed to stop blinking and stay on if you hold the brake pedal. The fact that this is not happening indicates a problem with the brake switch or the turn signal switch, assuming the fuses are all good, and you said they are.
When you have your emergency flashers on, the flashers are supposed to stop blinking and stay on if you hold the brake pedal. The fact that this is not happening indicates a problem with the brake switch or the turn signal switch, assuming the fuses are all good, and you said they are.
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5th Wheeling
Joined: Dec 2006
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The brakelight switch has one lead which is hot constantly. When you press the brake pedal the other wire is now hot as the switch opens. I keep hearing that the problem is probably in the trurn signal switch or harness.
MSEE
Joined: Apr 2004
Posts: 10,386
Likes: 35
From: Austin, TX
The procedure you described is correct. Based on process of elimination, it sounds like your turn signal switch is bad. The brake light circuit goes through the turn signal switch, and since the hazards test failed, it sounds like the switch is bad. Most times the switch is the culprit, not the actual harness. You'll need a steering wheel puller to get to the switch. The switch is different for tilt and non-tilt columns I believe, so make sure you get the right one when buying a replacement switch.
