Brake Light Switch ?
Thread Starter
Burning Brakes
Joined: Sep 2006
Posts: 1,242
Likes: 12
From: Kalispell MT
Brake Light Switch ?
Is the brake light switch at the pedal a Normally Open or a Normally Closed switch?
I'm chasing a tail light grimlin that has decided to pop up. I think my real issue is a ground at the rear.
Thanks in advance for the answers!
I'm chasing a tail light grimlin that has decided to pop up. I think my real issue is a ground at the rear.
Thanks in advance for the answers!
Le Mans Master
Joined: Jul 2000
Posts: 6,001
Likes: 112
From: Saginaw Michigan
I had one go bad that just wouldn't carry the tail light current. Checked good with a continuity meter. I just installed a new switch and tail light problem went away. (They aren't that expensive.)
Jim
Jim
Drifting
Joined: Sep 2006
Posts: 1,986
Likes: 21
From: Columbus MN
...when the pedal is released.
When think of a push button switch, I think, "Push for ON, release for OFF." The brake light switch operation is reversed from that, "Push for OFF, release for ON."
When you step on the brake, the pedal releases the switch, which closes.
When the brake pedal is released, the pedal depresses the switch, which opens it.
The switch is adjustable fore and aft. If the switch is too far forward, there isn't enough travel in the switch to close the circuit and turn the brake lights on. If the switch is too far aft, there isn't enough travel to open the circuit and the brake lights don't turn off.
If your brakes lights are not turning ON, try adjusting the switch aft if your fuse, ground, etc. are all good.
Hope that makes sense.
When think of a push button switch, I think, "Push for ON, release for OFF." The brake light switch operation is reversed from that, "Push for OFF, release for ON."
When you step on the brake, the pedal releases the switch, which closes.
When the brake pedal is released, the pedal depresses the switch, which opens it.
The switch is adjustable fore and aft. If the switch is too far forward, there isn't enough travel in the switch to close the circuit and turn the brake lights on. If the switch is too far aft, there isn't enough travel to open the circuit and the brake lights don't turn off.
If your brakes lights are not turning ON, try adjusting the switch aft if your fuse, ground, etc. are all good.
Hope that makes sense.
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,114
From: Crossville TN
Well, that even confused me. That switch is placed on the pedal linkage so that the switch is released when the pedal is depressed. The switch, therefore, is a Normally-CLOSED type of switch so that when the pedal is depressed (and the switch button is released), the brake lights are ON. Conversely, when the pedal is released, the switch is engaged and the brakes are OFF.
Drifting
Joined: Sep 2006
Posts: 1,986
Likes: 21
From: Columbus MN
Well, that even confused me. That switch is placed on the pedal linkage so that the switch is released when the pedal is depressed. The switch, therefore, is a Normally-CLOSED type of switch so that when the pedal is depressed (and the switch button is released), the brake lights are ON. Conversely, when the pedal is released, the switch is engaged and the brakes are OFF.
If the switch was normally CLOSED, then the circuit would be closed and the brake lights would be ON. The switch is normally pressed by the pedal arm, and the pedal arm pressing the switch keeps the circuit open.
I think you are speaking in terms of the switch externally (pressed or released), and I was speaking in terms of the switch internally (open circuit or closed circuit.
Le Mans Master
Joined: Aug 2006
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From: mount holly NC
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Team Owner
Joined: Jul 1999
Posts: 26,545
Likes: 46
From: Huntersville NC
so Ray Y, ya got it? 
When the plunger is pushed in, the brake lights should be OFF. When the switch is installed correctly above the brake pedal, it is pushed in by the resting brake pedal so the brake lights are off. When you step on the brake pedal, the plunger pops out and the brake lights should go on. So if the brake light switch is sitting on your kitchen table with the plunger extended, the switch should conduct electricity.
Here is my bubba-installed brakelight switch with the brake pedal pressing the button down which is keeping my brakelights OFF.
It is a little counter intuitive. If you didn't know any better you might think that when you push on the brakes, it pushes on a button that turns on your brake lights. But it doesnt work that way!
When the plunger is pushed in, the brake lights should be OFF. When the switch is installed correctly above the brake pedal, it is pushed in by the resting brake pedal so the brake lights are off. When you step on the brake pedal, the plunger pops out and the brake lights should go on. So if the brake light switch is sitting on your kitchen table with the plunger extended, the switch should conduct electricity. Here is my bubba-installed brakelight switch with the brake pedal pressing the button down which is keeping my brakelights OFF.
It is a little counter intuitive. If you didn't know any better you might think that when you push on the brakes, it pushes on a button that turns on your brake lights. But it doesnt work that way!
Last edited by PRNDL; May 15, 2010 at 03:38 PM.
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Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,114
From: Crossville TN
petes74ttop is correct. You designate a switch as normally open or normally closed by the state it is in when un-applied. The GM brake light switch is a 'normally closed' switch. When installed on the car and with the brake pedal released, the switch IS applied and is in the OPEN state. Thus, removed from the car it is in the "normally closed" state and that's how you would order such an item.
8th Gear
Joined: Jul 2007
Posts: 8
Likes: 0
From: Arnold MO
Unplugging the switch?
So if I read this correctly, if you unplug the brake light switch then the circuit is open and and the brake lights would turn on? 
I ask because my brake lights just stopped working this week. Hazards, directionals, running lights all work just fine. I unplugged the brake light switch and there was power from the white wire on the side heading to the signal switch. I then bridged the white and orange on the plug and still no brake lights.
Brake light switch GOOD.
Signal switch BAD.
Opinions?
Prior to the brake lights not working the directionals would not always turn off after returning to nuetral after completing a turn.
I ask because my brake lights just stopped working this week. Hazards, directionals, running lights all work just fine. I unplugged the brake light switch and there was power from the white wire on the side heading to the signal switch. I then bridged the white and orange on the plug and still no brake lights.
Brake light switch GOOD.
Signal switch BAD.
Opinions?
Prior to the brake lights not working the directionals would not always turn off after returning to nuetral after completing a turn.
Last edited by flybigrc; Jul 21, 2010 at 01:46 PM.
Drifting
Joined: Sep 2006
Posts: 1,986
Likes: 21
From: Columbus MN
So if I read this correctly, if you unplug the brake light switch then the circuit is open and and the brake lights would turn on?
I ask because my brake lights just stopped working this week. Hazards, directionals, running lights all work just fine. I unplugged the brake light switch and there was power from the white wire on the side heading to the signal switch. I then bridged the white and orange on the plug and still no brake lights.
Brake light switch GOOD.
Signal switch BAD.
Opinions?
Prior to the brake lights not working the directionals would not always turn off after returning to nuetral after completing a turn.
I ask because my brake lights just stopped working this week. Hazards, directionals, running lights all work just fine. I unplugged the brake light switch and there was power from the white wire on the side heading to the signal switch. I then bridged the white and orange on the plug and still no brake lights.
Brake light switch GOOD.
Signal switch BAD.
Opinions?
Prior to the brake lights not working the directionals would not always turn off after returning to nuetral after completing a turn.
If you bridged the wires and the BLs did not light, then you have to trace the circuit from there to find the circuit problem IMO. The switch still may be bad.
