Author Topic: Brake Lights  (Read 9671 times)

Offline Hank Hill

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Brake Lights
« on: January 18, 2008, 02:28:57 PM »
All lights/signals work on my truck except fot the brake lights.Also the brake lights on my trailer dont work now either. Truck is a 81 GMC. All fuses seem to be working on the fuse box although there are circut breakers there that I didnt check. Have no idea when the brake lights stopped working.
Have not checked the bulbs because I cant see all the bulbs being blown at the same time.
Backup lights work to.
How do brake lights work? On the brake pedal I cant find any electrical conections that would engage them. Cant find any fuse marked brake lights.
On my 87 when you press the brake pedal it moves away fom two electrical connections(breaks the circut?) but on my 81 there are no connections. There is the bracket there for two connections(switches) but no wires or switches like on my other truck?
Here is the thing though. I have had this truck forever. I used to have break lights.Well im pretty sure I had break lights? I must have had break lights. Yes im sure I did. Well pretty sure. Well it had to have had break lights at one time. Anyway I didnt remove the switches or wiring so they must not have ever been there? Right? Im totally confused. So do the break lights work differently on a 87 than they do on an 81?
Any ideas about how I could fix them? Thanks

Offline Hank Hill

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Re: Brake Lights
« Reply #1 on: January 18, 2008, 02:40:08 PM »
Man I looked everything over and that truck must have been without brake lights since I had it. The factory switches that disconect when you press the brake pedal are gone, a long with all the wireing.
So I guess my question is now how do I wire up brake lights from scrath? Example I need two of those switches for the brake linkage but then where do I hook the wires to?
« Last Edit: January 18, 2008, 04:40:21 PM by Hank Hill »

Online VileZambonie

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Re: Brake Lights
« Reply #2 on: January 18, 2008, 04:44:16 PM »
#1 forget about your trailer until you figure out your base lighting ckt. Always go to the source. These trucks only have two brake lamp bulbs and the possibility of them both being out is there. 4 screws and you can check a bulb to see. If you have no B+ at the lamp socket when the pedal is depressed check the stop lamp switch. It's located on the brake pedal arm bracket. You can jump the switch and see if the lights come on or try adjusting the brake lamp switch. Do you have a 12V test light?
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Offline Hank Hill

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Re: Brake Lights
« Reply #3 on: January 18, 2008, 07:00:18 PM »
See the stop lamp switch on the pedal linkage isnt there.
I know what happened. This truck originaly had cruise control. When the criuse control was removed so was the brake light switch/wireing.
One switch on the brake pedal was for the cruise and the other one was for the brakes.  shows the switches for the brake lights are different depending on if the truck had cruise control. Guess I now need a switch for a truck with an auto transmission  and no cruise control. But how do I wire it?

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Re: Brake Lights
« Reply #4 on: January 18, 2008, 07:09:55 PM »
The brake switch wiring would have to have been cut in order to have been removed. Why would someone cut it out? Are you sure it's not there?
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Offline jonkmbll89

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Re: Brake Lights
« Reply #5 on: January 18, 2008, 07:12:29 PM »
The wire that hooks to your switch that goes out to your tail lights should still be there. Just hook that wire to your new switch and run costant hot wire from your fuse block to the other side of your switch and you should be back in business.
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Offline TexasRed

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Re: Brake Lights
« Reply #7 on: January 18, 2008, 09:36:23 PM »
Do you have a lockup transmission?

Offline Hank Hill

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Re: Brake Lights
« Reply #8 on: January 19, 2008, 03:26:47 PM »
I replaced the TH350 when the houseing broke with a 350c lockup but there are no wires running to it.
As far as whats there for break light wires im just going to have to take that dash a part to get a better look because I cant see any cut wires from just looking up underneith the dash.
Were getting a snow storm right now so this repair is going to have to wait.
A buddy has a shop and he also has a junked GMC truck with no air and an auto transmission in it. According to parts catologs if you have air, criuse or an auto transmission you use a different brake light switches. My truck originally had air/ power doors, criuse but all of this stuff was taken off. Anyway his switch and hopefully his wire harness should hopefully fit my truck.
Anyway when my buddy gets some of his current projects done im going to take my truck over and use his shop. Will let you know how I make out. Thanks for the tips.

Offline jonkmbll89

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Re: Brake Lights
« Reply #9 on: January 19, 2008, 07:05:23 PM »
Your lock up convter wire should run through your brake switch. So when you press the the brake petal the trans will down shift one gear and when you let off of the petal the trans will shift back up.
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Offline Fordeatinz71

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Re: Brake Lights
« Reply #10 on: January 19, 2008, 10:17:37 PM »
air shouldn't matter.  the only options that might matter to the brake light switch are cruise and auto/manual...

look at your wiring harness in the rear...at the taillights.  one of those wires are to your brake lights...i think it's the brown one.  anyhow, you can narrow it down with a multimeter...my Haynes manual is unclear but i think it's the brown one.  anyway, just take your multimeter and check for voltage with your parking lights on.  the other wire you should see is black...that's a ground.  the "odd man out" is your brake light wire.  just carefully (it's gonna be a pain) start tracing it.  then you'll figure out where it "ends" or if it does at all...



ok, now, if you wanna check from the other end, look under the dash around where the brake pedal mounts.  there should be two wires, one being an orange which is hot all the time (coming from the fusebox) and the other should be white (i keep saying "should be" because i don't have a factory service manual, just this Haynes POS).  if you see these two wires grouped together then that is the connection.  then you'll just need a brake light switch.  if you still have the factory connector (they can hide on ya) the you are most likely gonna have to get the brake light switch for the options it originally had, so the connector will hook up, unless you are gonna cut and splice it. 

hope this helps, good luck!
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Re: Brake Lights
« Reply #11 on: January 19, 2008, 10:24:08 PM »
Your lock up convter wire should run through your brake switch. So when you press the the brake petal the trans will down shift one gear and when you let off of the petal the trans will shift back up.

The brake switch will not cause it to downshift it will simply de-energize the TCC solenoid.
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Offline jonkmbll89

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Re: Brake Lights
« Reply #12 on: January 20, 2008, 09:46:54 AM »
Your lock up convter wire should run through your brake switch. So when you press the the brake petal the trans will down shift one gear and when you let off of the petal the trans will shift back up.

The brake switch will not cause it to downshift it will simply de-energize the TCC solenoid.

Cool
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Offline Hank Hill

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Re: Brake Lights
« Reply #13 on: January 21, 2008, 10:28:22 AM »
Hey thank you all very much.

Offline Dragon

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Re: Brake Lights
« Reply #14 on: January 21, 2008, 11:30:05 PM »
Weither you have air or not, doesn't make a difference....  A Cruise Control switch is a two-stage switch, front half controls the Brake Lights, and the rear half controls the Cruise Disable..  When you add overdrive or a Lock-up converter to the mix, another stage is added(In some cases it can be just piggy backed off of one other halves of a two stage) to the middle of the switch....

Non Cruise, Automatic Switch

Non Cruise, 4spd Auto/Auto wih Lock Up Converter

3spd/4spd Auto, With Cruise
(Corrected so as to not leave Fordeatinz71 out ;D)

Non-Cruise, with Manual Trans.


Those are the majority of the different switches available, with a few exceptions...  In some of the Older trucks with Cruise, a seperate Stop Lamp Switche was used for each feature(Ie Brakes got one, and Cruise got another)..  Some Early 4spd/Lock-up Trans models, employed one  two stage switch for the Cruise and Brakes, with a single stage switch pulling duty for the TCC...
« Last Edit: January 23, 2008, 12:35:20 AM by Dragon »
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