Electrical Brake Light Switch

Shane8996GTLX

Active User
Oct 22, 2017
61
4
18
Illinois
Alright guys in my last ditched effort to avoid a dealer fix I thought I'd create an account. My brake lights stopped coming on last night when I accidentally tugged on a wire thinking it was my boost tube. I did my research and got under the dash. The pigtail and switch where still intact. I went to AutoZone and bought both thinking I damaged them. nope! Still no luck after the install. The lights still come on, the Hazzard lights and turn signals. Bulbs all work. There was a black wire crimped on the pigtail with my idea where it went. I have not seen anywhere else where this wire is included on the net or the knowledge of AutoZone lol. Please help.
 
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Alright guys in my last ditched effort to avoid a dealer fix I thought I'd create an account. My brake lights stopped coming on last night when I accidentally tugged on a wire thinking it was my boost tube. I did my research and got under the dash. The pigtail and switch where still intact. I went to AutoZone and bought both thinking I damaged them. nope! Still no luck after the install. The lights still come on, the Hazzard lights and turn signals. Bulbs all work. There was a black wire crimped on the pigtail with my idea where it went. I have not seen anywhere else where this wire is included on the net or the knowledge of AutoZone lol. Please help.
"NO" idea where it went? Ford often uses black for grounded conductors. Try touching that black ne to a rounded part, see if that's the problem. imp
 
I meant no. I tried to apply it to a ground source and no such luck. The new pigtail from AutoZone has one solid green wire and green/red stripe. Matched green/red with green/red and solid green with red/green stripe.
 
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I meant no. I tried to apply it to a ground source and no such luck. The new pigtail from AutoZone has one solid green wire and green/red stripe. Matched green/red with green/red and solid green with red/green stripe.
Then we need to consult the wiring diagrams. Otherwise, yer just kickin' about. imp
 
I wasn't aware it needed a ground wire and so I'll have to get back to you on that. I'll need to switch it around to the other wire. As of last night no. It does show power from the fuse panel under the hood. 96 mustang GT.
 
For the 1996 model year the brake on/off (BOO) does not have or need a ground. The wire colors are LG/R (source) and R/LG(load).

The BOO switch is a simple on/off switch. As such the order of the wires do not matter. So if you had to splice in the BOO switch don't waste your time reversing the wires.

But are you certain that you are working with the BOO switch?

Once you have confirmed power into the switch, the next step is to confirm power out of the switch. IF there is power out of the switch AND the 3rd high mounted brake light does NOT work, then the problem lies elsewhere (not the BOO switch).

IMO your next test should be for power out of the BOO switch with the pedal depressed. Will also need to know IF the high mount 3rd brake light is working.

If there's power out of the BOO and the 3rd high mount brake light does not work (bulbs tested good), the next test should be to CONFIRM the ground path all the way back to battery negative.
 
I will have to look into this this evening when I get home. I know there is polarity to at least one part of the brake switch terminal when I select the option to beep on the meter. If you mean boo switch as in the brake light switch that's what I've been working on.
 
@wmburns
Maybe save getting into that nasty-located BOO switch:

High-mount stoplamp is fed by a different fuse than the Multi-Function Switch, which in turn feeds the turn signal lamps and hazard lamps function. Thus, a blown fuse for High-mount would kill all stoplamps operation. This is from '04 Explorer wiring diagrams, but Mustang may be similar. Stoplamps are fed by F-25 in the Battery Junction Box, underhood, 15 amps, while the other lamp functions are fed by two fuses in the Central Junction Box, in car. The fuse numbers will no doubt be different.

Just a thought. imp
 
FWIIW, the power for the 3rd high mounted brake lights do NOT go through the multi-function switch. This is why it's good to know the status. Details such as this help to rule out/in a problem with the multi-function switch.

IF the high mounted 3rd brake light does not work, then focusing first on the multi-function switch isn't a good use of your trouble shooting effort.
 
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I went back under the trunk and noticed there were no bulbs even in the third brake light so I need to get some and recheck. For the MF Switch I got it available to look at if it needs assessment. So if the MF Switch does come to be the culprit how do I check it. I reassessed the junction boxes under hood and in car with no blown fuses. I see no frayed wires. I rechecked the volts which are active under the hood to the select spot. There is activity to one spot on the BOO. There is flowing voltage to the fuse area number 9. So I am confused to what to look at next.
 
I went back under the trunk and noticed there were no bulbs even in the third brake light so I need to get some and recheck. For the MF Switch I got it available to look at if it needs assessment. So if the MF Switch does come to be the culprit how do I check it. I reassessed the junction boxes under hood and in car with no blown fuses. I see no frayed wires. I rechecked the volts which are active under the hood to the select spot. There is activity to one spot on the BOO. There is flowing voltage to the fuse area number 9. So I am confused to what to look at next.

If I could text you this would be easier. If not that's ok. Heading to work soon. Glad I got 3 cars lol!
 
When you can afford it I highly recommend the Factory Manual with supplements. The schematics and trouble shooting areas are indispensable to me(first thing I buy after car purchase) and you can even get your money back( I have made a profit before too!) after you sell the car. Alas mine is for 2002. Wmburns can help you out on this I think.