1992 Ford Ranger Brake lights on with headlights

1992 FORD RANGER
178,000 MILES • 6 CYL • 4WD • MANUAL
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PUGGLAS
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  • 2 POSTS
My brake lights come on when I turn on the headlights. They operate fine when the headlights are off. Several years ago, a friend wired in a harness for a boat trailer, they were working fine until recently. Is this the indication of a bad ground, and if so how do I locate the problem?
Aug 21, 2009 at 8:20 AM
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RASMATAZ
  • ✓Experienced Mechanic
  • 75,988 POSTS
If its a ground problem the light will not come on-inspect the trailer wiring harness -sounds like the running and brake lights are shorted together.
Aug 21, 2009 at 8:32 AM
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JDL
  • ✓Experienced Mechanic
  • 16,098 POSTS
Hello, I'd probably check the brake switch, the light green wire should not be hot unless you step on the brake. I believe the lower brake lites and turn signals use the same circuit and bulb filament, just not at the same time. They are wired through the multifunction switch.

If the ground for the tail lites is faulty, that circuit might try to ground through the turn/brake circuit?
Aug 21, 2009 at 8:34 AM
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