Gents, I really appreciate this site more than you can know. I recently replaced my brake booster and master cylinder, as when I started the car with my foot on the brake i could hear what sounded like air rushing through the brake booster area. I pulled off the old booster and it looked original from the factor, rusted all the rubber torn apart. So far so good (outside the 10 hours it took me to complete this task). I test drive my car, brakes are great but I have no brake lights. I went back over my work, as I had to lower the steering column to gain access to some of the nuts behind and above the brake pedal. Doing some troubleshooting, when I rotate the switch by hand with everything hooked up, the brake lights come on. When I just press the brake pedal, the do not illuminate. I followed my shops manual during this excursion, with much difficulty, so my question is as follows: What forces the brake switch to rotate when depressing the brake pedal to create the path for electricity to go to the brake lights? What am I missing? I have a 1989 Mustang GT. Thank you for your help.
Resolved Brake light switch
- Thread starter Alabama
- Start date
I watched that earlier in my troubleshooting. nice having all that room with the mock up but understand the purpose of the mock up for explanation sake. I followed that to a T, guessing if my brake lights work when I rotate the brake switch by hand but not when I push my brake pedal that my brake switch needs replaced?
Wait a minute, what do you mean 'rotate' the switch?
It's kind of a 'plunger ' type deal, you can see (I think anyway) how it works when pushing the pedal.
It's kind of a 'plunger ' type deal, you can see (I think anyway) how it works when pushing the pedal.
Scrapla347
Active Member
So I replaced my booster and reused my brake light switch. My brake lights were stuck on and I found that the wiring was all bunched up. Have you crawled back under there and had a look? I don't understand the rotate part because it's attached to the pedal and compresses so maybe it's on cock eyed or something?
Kind of weird i know. When I have everything installed: the brake switch, brake booster both on the pedal, connector on the switch, I depress the pedal and no brake lights illuminate. Same set up as above, without depressing the brake pedal, i put my hand on the brake switch and rotate it up or down, brake lights come on. Based off the above, I was under the impression the brake switch should hit the forward most steering shaft mount when the brake pedal is depressed, causing the switch to rotate on the booster piece, depressing the metal and spring, creating a path for electricity to go to the brake lights. I might be way off base here with this and just have a crap switch that just needed to come off the brake pedal to quit working, but I don't see how a switch just sitting on the knob of the brake pedal and should move when you depress the pedal, Newton coming into action here, objects at rest and so forth, allowing the path for electricity to go to the brake lights. My set up is exactly the same as the video from @AeroCoupe and how specifically depressing the brake pedal activates the switch may be a bridge too far for me to understand. Hope this helps.
I did play with it a bit today. Wires are routed properly and not binding on any of the frames under there. I also tried to install it a few different angles but it always ended up pointed straight back and inline with the booster arm. Seems like when I rotate the switch by hand, it depresses the metal and spring inside the switch creating that bridge for the voltage to continue back to the brake lights. Hope this helps. Thank you.
Your switch works, it's installed wrong. Switch does not 'rotate'. You have it upside down or backwards,.without a pic I can't tell what's amiss, I understand a pic in that area is challenging.
Scrapla347
Active Member
I also heard some boosters have a different diameter hole in the mounting arm. So the part that slides onto the brake pedal might be a different thickness so that plastic washer that came off the OEM one might be too small or too big. I put my phone on front facing camera and laid it under my peddle assembly on record mode. I then pressed the brake pedal by hand a few times. I then put the video on my computer to watch it and that's how I noticed the mistakes I made on the reinstall. It's all a frustrating mess.
First and foremost, don't crucify me for the surface rust on the structure under the dash, I haven't gotten there yet. They are attached including a video for the movement to validate the booster arm with plastic bushing fits appropriately on the knob of the brake pedal, as @Scrapla347 suggested above. Thanks again for your help.
Attachments
Video is an .mp3 file which is just sound.
So by the looks of it you do not have the cruise control piece on the brake pedal so you need two of the white plastic washers on the brake pedal stud before you install the switch. You should also have a plastic bushing in the brake booster rod which I think is installed but hard to tell. You have the switch oriented correctly so that is not an issue.
If you can try and upload a video or what the switch looks like orientation wise when the pedal is depressed.
So by the looks of it you do not have the cruise control piece on the brake pedal so you need two of the white plastic washers on the brake pedal stud before you install the switch. You should also have a plastic bushing in the brake booster rod which I think is installed but hard to tell. You have the switch oriented correctly so that is not an issue.
If you can try and upload a video or what the switch looks like orientation wise when the pedal is depressed.
I have tried to upload the video but I don't know a format that this site will accept. When put together, I put the second white spacer on the outer edge next to the clip that holds stack up on the stud. The brake booster I installed is: https://lmr.com/item/LRS-2005CB-K/mustang-50-resto-1993-cobra-style-brake-booster-kit-87-93. Was told it is a direct replacement for stock, will eventually upgrade to the rear wheel 4 lug disk brake system, but is the piece from the booster to the pedal attachment the same as stock? I would think they would have check that. Could it be something downstream from the switch? I will check the schematics to see how the signal runs from the switch back to the brake lights, but that almost makes no sense as if I rotate the switch, my brake lights come on. If you know a way to upload the video, please let me know. It won't let me upload an MP4. Thanks again.
It looks like your brake switch has a problem. When the pedal moves forward it should compress slightly which is what completes the circuit in the switch. The plate part of the brake light switch right behind the brake pedal rod should move and compress that spring. Watch this video:
View: https://www.youtube.com/watch?v=nbNPbCCuHlM
It looks like the plate in yours is bent and causing it to jam up and not move.
View: https://www.youtube.com/watch?v=nbNPbCCuHlM
It looks like the plate in yours is bent and causing it to jam up and not move.
Scrapla347
Active Member
Great pics. The electrical connection portion of the switch is suppose to face towards you if I'm not mistaken. There should also be a red clip that holds it all in place.
View: https://youtu.be/2Gpib1v4wLM?si=Ij5IzKRkjUQdHpQL
Thank you for the information. The pictures I posted wasn't with it all put together as I was troubleshooting, assembly and disassembly. Thank you again.
This video is what fixed my brake issue. It explained, specifically with the plastic hat bushing, how it compresses the light switch causing the brake lights to illuminate. I measured my old and new plastic hat bushings, not a lot of discrepancies there. What i did do was take a dremmel tool with a sanding drum and sanded my booster arm that connects to the brake pedal allowing for this movement to compress the plate enough to illuminate my brake lights, but not so much that they illuminate without requiring brake pedal movement (not coming on just sitting there). Thank you so much for this. Now on to my next project, engine vacuum lines and connections. Thank you so much again.
Scrapla347
Active Member
Yea my brake lights are stuck on and only go off if I reach up under there and move the the harness around. After market parts store booster so I need to get back under there and see what's up.
Anyone know where I can get the striker plate for my brake pedal that disengages the cruise control??? My car is equipped for cruise, I have the switch there for cruise release, just not the striker plate. Thanks again.
I wonder if a 94/95 part would work.
www.fordonlyparts.com
@Mustang5L5 - Do you have one of these brackets where you can take a look and see if there is a part number on it?
1994-1995 Ford Mustang Brake Pedal Cruise Control Cancel Switch Bracket F4ZC-9C962-AA
In Good Working order from a 1994-98 mustang
www.fordonlyparts.com
@Mustang5L5 - Do you have one of these brackets where you can take a look and see if there is a part number on it?
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