1994 GMC SIERRA TROUBLE WITH BRAKE LIGHT SWITCH

  • Tiny
  • lmriggs
  • 1994 GMC Sierra

Brakes problem
1994 GMC Sierra V8 Two Wheel Drive Automatic 94000 miles

I just replaced the brake switch on my pickup following the instructions found here: http://www.2carpros.com/forum/1996-gmc-sierra-c1500-brake-light-switch-replacement-vt52484.html and after replacement, it still doesn't work. In fact, I don't even understand how the switch can work. If the brake light switch AND the plunger that goes into the master cylinder AND the brake pedal is moving simo, how can the brake pedal push the button that turns on the lights (without the switch being rigid and attached seperately from the rest of the compodents)? In other words, everthing is moving together.

Is there a trick in getting this replacement to work?

Tuesday, September 28th, 2010 AT 7:37 PM

14 Answers

  • Tiny
  • bluelightnin6
  • Expert
  • 17,063 posts

Make sure you have switch adjusted correctly. If new switch didn't fix issue than check wiring. If wiring is good than suspect faulty turn signal switch as the brake light wiring runs through the signal switch.

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Tuesday, September 28th, 2010 AT 9:04 PM
  • Tiny
  • lmriggs
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Thank you for your reply!

I can get the switch to work manually (with my fingers) but not while it is mounted. Also, my turn signals work just fine.

You mentioned 'adjustment'. I don't see any way to adjust the switch. It simply mounts in a prefixed manner and there is no adjustment screws, etc.

Again, thank you!

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Wednesday, September 29th, 2010 AT 9:47 AM
  • Tiny
  • bluelightnin6
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http://www.2carpros.com/forum/automotive_pictures/261618_Noname_2718.jpg



http://www.2carpros.com/forum/automotive_pictures/261618_Graphic_704.jpg

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Wednesday, September 29th, 2010 AT 1:09 PM
  • Tiny
  • lmriggs
  • Member

Good day, again.

The pix you have attached is the wrong switch. I failed to mentioned that I have a Sierra PU. The capture I have attached is the correct switch.


http://www.2carpros.com/forum/automotive_pictures/577797_Capture_1.jpg

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Wednesday, September 29th, 2010 AT 1:53 PM
  • Tiny
  • bluelightnin6
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Diagram I posted is for the sierra pickup, do you have cruise control?

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Wednesday, September 29th, 2010 AT 2:57 PM
  • Tiny
  • lmriggs
  • Member

Yes I do. And it won't disengage w/o this switch working properly. That's scarry!

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Wednesday, September 29th, 2010 AT 3:14 PM
  • Tiny
  • bluelightnin6
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CC shouldn't work at all with a malfunctioned brake switch. If you have CC than your switch should look just like the diagram I posted, are you certain you got the correct replacement?

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Wednesday, September 29th, 2010 AT 3:17 PM
  • Tiny
  • lmriggs
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CC wil engage but won't disengage by tapping the break pedal. The unit I am trying to put in is indentical in shape to the unit I took out.

Go to the below link and this is the pix of the exact setup I have that I am working with:

http://www.2carpros.com/forum/1996-gmc-sierra-c1500-brake-light-switch-replacement-vt52484.html

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Wednesday, September 29th, 2010 AT 3:24 PM
  • Tiny
  • bluelightnin6
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Okay, heres how you adjust that type of switch then. There should be a small switch nipple that rests against the brake lever arm. That can be adjusted by depressing it hard until it clicks into another position. Try to adjust it that way and see if it helps.

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Wednesday, September 29th, 2010 AT 3:28 PM
  • Tiny
  • lmriggs
  • Member

If you look at my pix, you will see a hint of a gold-colored 'trigger' (inside the hole) that lays against the pivot point on the brake pedal. When the pedal is depressed, it is suppose to push the gold 'trigger' into a plastic slide-switch which, inside the switch, engages/disengages up to six contacts.

I tore the old swith apart (I'm good at that) and there is no intermittent steps that the slide can stop at. The plastic spring-loaded slide only slides forward and backward along a track doing it's work. There is no adjustments at all on this.

In fact, it is an extremely simplistic (cheap) switch.

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Wednesday, September 29th, 2010 AT 3:46 PM

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