Brake Lights???
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Joined: Jun 2015
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Brake Lights???
This may be a rookie question but....my son just received a 1966 F100 from his grandpa and I noticed that the brake lights aren't any brighter than the parking lights. The lights do come on when the brakes are pressed. But, when the parking lights are on, there's no indication that the brakes are being pressed (the light doesn't get brighter). The bulb looks like it has two distinct filaments but there's just two wires going to the lights. Do I have a problem here or is this normal?
Senior User
Joined: Nov 2011
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From: Yelm, WA
There are only 2 wires to the tail light. One is the tail light (running light) and the other is the brake light. The body acts as the ground. First check the fuse panel under the dash for a blown fuse.
Pick up a test light probe at the auto parts store. Attach the one wire to a good ground and probe both wires to see if you have power to both. if so make sure the socket is grounded to the body. Often rust messes up the ground connection.
If there is no power to the brake wire check the brake light switch. It could be it is bad or the wiring in between.
Good grounds are very important as "back feed" can cause all sorts of interesting problems
If you're lucky the wiring hasn't been messed up by a previous owner.
Pick up a test light probe at the auto parts store. Attach the one wire to a good ground and probe both wires to see if you have power to both. if so make sure the socket is grounded to the body. Often rust messes up the ground connection.
If there is no power to the brake wire check the brake light switch. It could be it is bad or the wiring in between.
Good grounds are very important as "back feed" can cause all sorts of interesting problems
If you're lucky the wiring hasn't been messed up by a previous owner.
Last edited by Old Rusty; Jun 2, 2015 at 11:01 AM. Reason: missed a point
Senior User
Joined: Oct 2014
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From: Lynnwood, WA
It could also be that someone in the past did a hack-job and mis-wired the terminals to the sockets and the brake light filament is acting as your running light and the brake lights are wired to the running light filament. This running light filament would not add much more light to an already lit brake light filament in the same bulb.
The test for this is to apply the brakes first, see how bright they are. Then while holding the brakes down turn on the running lights. If then they now appear to get brighter, the wires at the sockets are reversed.
The test for this is to apply the brakes first, see how bright they are. Then while holding the brakes down turn on the running lights. If then they now appear to get brighter, the wires at the sockets are reversed.
Post Fiend
Joined: Dec 2013
Posts: 5,967
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From: Philly Suburbs, PA
actually the break light/turn signal filament is brighter than the running light filament. I thought originally that it got brighter if you hit the break lights because both were burning so I tested it. Not so. Actually different brightness.
Fleet Owner
Joined: Jun 1999
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From: Creedmoor, North Carolina
John
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