Electrical Oddity
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Posting Guru
Joined: Jan 2001
Posts: 2,357
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From: S. Mississippi
Electrical Oddity
I drove my truck for the first time in several months tonight... whenever you press the brake pedal the highbeams turn themselves on and go right back off when the pedal is released, my questions is it the dimmer switch, or am i completely off
New User
Joined: Jan 2008
Posts: 0
Likes: 24
Electrical Oddity
You didn't a say what truck you have.
I'm sure the wiring is different over certain years.
Powwer goes threough> Headlight switch> Brake light switch,Dimmer switch.
Dennis
Please Don't Ask Me Any Tough Questions As:
"I'm Saving My Memory For When I Develop Alzheimer's"
78 F-150 429CJ,Silver
w/Explorer Pkge.
641/2-Mustang 260,Pre-World's Fair Car.
64-Fairlane500 S/C waiting for a 390-4spd.
68-Mustang 289-Sunlit Gold 80,892Mi
78-Buick LeSabre 403 4V
84 Volvo DL Wagon
I'm sure the wiring is different over certain years.
Powwer goes threough> Headlight switch> Brake light switch,Dimmer switch.
Dennis
Please Don't Ask Me Any Tough Questions As:
"I'm Saving My Memory For When I Develop Alzheimer's"
78 F-150 429CJ,Silver
w/Explorer Pkge.
641/2-Mustang 260,Pre-World's Fair Car.
64-Fairlane500 S/C waiting for a 390-4spd.
68-Mustang 289-Sunlit Gold 80,892Mi
78-Buick LeSabre 403 4V
84 Volvo DL Wagon
Freshman User
Joined: Jan 2002
Posts: 32
Likes: 0
Electrical Oddity
Sounds like you have an ground problem in the cab .
Look for a ground strap going from the frame to the cab.
Its probley lose. That would explain it suddleny working.
My tail lights would come on off depemding on what bumps I hit. Checked
the ground going to the cab and it was lose.
Look for a ground strap going from the frame to the cab.
Its probley lose. That would explain it suddleny working.
My tail lights would come on off depemding on what bumps I hit. Checked
the ground going to the cab and it was lose.
New User
Joined: Feb 2002
Posts: 18
Likes: 0
From: Lenexa USA
Electrical Oddity
YES check for bad grounds, I had an ignition problem once and I tore the whole dash apart looking for the reason I could hear sparking in my distributor (while the engine was off!) every time I turned my windsheild wipers on. turned out to be one lousy loose ground on the firewall that only took 5 seconds to fix. unfortuneatly it took me hours to put my dash back in.........
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Fleet Owner
Joined: Aug 2001
Posts: 29,941
Likes: 46
From: Drummonds, TN USA
Electrical Oddity
Check the point in the firewall where the wires go through and see if the rubber grommet that protects the wires from the metal edge beneath is shot. It sounds to me like you have a pair of bare wires allowing the 12 volt brake light signal to get to the high-beam system.
There are not many places where these wires are next to eachother (I hope), but that's where I would be looking. Especially under the dash itself...
But I'm not sure how a ground would affect the switches. I'll have to look at it in the manuals.
You should have a ground from the engine block to the firewall, and another to the frame. Make sure of them, especially if you have done a body lift.
There are not many places where these wires are next to eachother (I hope), but that's where I would be looking. Especially under the dash itself...
But I'm not sure how a ground would affect the switches. I'll have to look at it in the manuals.
You should have a ground from the engine block to the firewall, and another to the frame. Make sure of them, especially if you have done a body lift.
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