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?

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

14 Replies

Tiny
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
Tiny
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Double post

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Wednesday, September 29th, 2010 AT 4:42 PM
Tiny
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Sorry, I'm not sure what I'm doing wrong with this post.

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Wednesday, September 29th, 2010 AT 4:45 PM
Tiny
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Ok I see whats going on here, you have this posted as a 1994 but the switch you are showing me is the newer style such as 1996 sierra. The newer style does not have adjustments. With the brake pedal in the relaxed position (no pressure applied to the pedal), the contacts of the switch should be mounted up against the pedal stop on the pedal housing. When pressure is applied to the brake pedal (as if braking), the contacts of the switch "close" thus closing the circuit and energizing the brake lights.

Is your switch positioned properly. Such that the contacts of the switch are positioned up against the pedal stop?

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Wednesday, September 29th, 2010 AT 5:04 PM
Tiny
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OK boys and girls. I have figured it out.

When I installed the new switch, somehow I cocked the gold trigger -- it came out of it holder. In this position, it was not pushing on the slide-switch properly and therefore, would not engage the stop lights.

I took it off again, found the problem, fixed it and reinstalled it. It is working just fine now. I have no idea how I did this but, once again, I screwed something up.

By the way, I went to a different vender (Checkers as opposed to NAPA) and they also pulled the same switch. So I know this is the right switch for that year but it probably covers several years including the '96 that you just mentioned.

Thank you very much for your efforts. I will use the forum again and I will donate next time.

Also, anyone changing this switch, you can save yourself a LOT of trouble by dropping the steering column down. It has only two nuts and it makes the switch much more accessible . Be careful to disconnect the small cable that goes to the shift indicator -- or you'll break it and compound your problem. Go to the below link for an additional discussion on this:

http://www.2carpros.com/forum/viewtopic.php?p=1003714#1003714

Once again, thanks for your trouble!!!

Lee

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Wednesday, September 29th, 2010 AT 6:09 PM

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