Brake lights mystery

[abcducati]

O.K. Hive mind, I've hit a wall and need some help/direction on how to proceed.
So my wife was backing our '04 XLS out of the driveway yesterday morning when I noticed that the brake lights were not coming on. As in NONE of the brake lights - left, right or high-mount center. Got her to work and came back to figure out what was wrong, starting with the obvious culprits. Checked the fuse (it was good, but replaced it with a brand new one anyway), then checked the brake light switch. This is where things get interesting. I went to one auto parts store, and the switch they tried to sell me looked nothing like what I have. I went down the street to a different shop, and the first part the clerk showed me looked nothing like mine. At this point I go out to the truck and remove the switch it has and take it in with me to show them exactly what I need. Different clerk helps me and gets me the right part. I go out to the parking lot and replace the switch and...still no brake lights. The running lights, turn signals and hazards all work fine, just no brake lights when the pedal is depressed. I also checked the bulbs this morning, but why would the flashers work and not the brakes if it was the bulb. If I'm checking for a short, where exactly should I be checking, as again, the flashers/hazards are working fine. Is there possibly another fuse or relay I need to check? Any help would be greatly appreciated.
Thanks in advance!

UPDATE: See my update below, as I had found the culprit, but am now back where I started after the fix.

 

[TechGuru]

Did you check fuse #25? Are you sure the bulbs are good in the high mount? Because if it were a problem with the multifunction switch the high mount would still work as it bypasses the multifunction switch.

 

[abcducati]

Did you check fuse #25? Are you sure the bulbs are good in the high mount? Because if it were a problem with the multifunction switch the high mount would still work as it bypasses the multifunction switch.

View attachment 426392

Yes. Fuse and all of the bulbs, and they were all fine, but I replaced them anyway I also checked all of the fuses indirectly related to the brakes (ABS and IVD module fuses), and even though they were o.k. I replaced them as well. I had a friend who is a mechanic take a look at it, and he checked everything I did. He also checked the wiring with a test light to confirm continuity, and at one point thought there was an issue between the pedal (brake switch) and the main harness, as the hazards, turn flashers and running lights were all still working fine. He then had me start the truck up and out of the blue I have working brake lights again. I mentioned that the MFS was being replaced this week (to resolve my high-beams not working), and he said that it could be a fault with it. I mentioned the part about how the third brake light was supposed to get power all of the time, and he said that it could still be the MFS because of how it interrupts the signal to the brake lights when both the pedal and turn signal are active. We also checked the wiring to the master cylinder and a switch next to it in the engine bay.
For now, I have working brake lights, and will continue monitoring the situation in case the problem reoccurs.

 

[TechGuru]

MSF does not affect the 3rd brake light though. Are you sure the bulbs are good in the 3rd brake light? I upgraded mine to LED.

Pardon Our Interruption...

 

[John9o9]

Mine had same issue I replaced the brake light switch the one they give is a update one doesn't look like old one. Will need to cut old harness and wire in New one

 

[mountaineer2004]

Are you sure the bulbs are good in the 3rd brake light? I upgraded mine to LED.

Pardon Our Interruption...

I bought these but they were not plug and play. Too big to fit it where the old ones were.

 

[TechGuru]

I bought these but they were not plug and play. Too big to fit it where the old ones were.

Fit mine just fine.

Sounds like you didn't take it apart correctly. You take it apart at the red plastic side not the rear side. They won't fit though the mirror reflectors from the back, you have to put them in from the front.

 

[abcducati]

UPDATE: So after months of checking EVERY SINGLE WIRE from the bulbs to the switch, the problem turned out to be a broken wire right where it went into a three-way junction/plug along the positive/hot(?) wire from the firewall to the brake switch on the pedal arm. Had to do some MacGyver-ing to said plug to get the wire to re-connect to the plug, only to have it come apart again. The area had some prior black/scorching around it, and it was very brittle. I thought that maybe by taking the three-way junction out and splicing the wires all together would be a work-around, but now I'm back to square one. I've attached a pic of the section of wire I cut out, along with what the plug/box pieces look like.

My new question is this: what are the two branch-off wires/little boxes for, and is it possible to bypass them and just run a bypass wire strait from the firewall to the brake pedal switch, or are they necessary in some way?
I may just have to go to a junk yard and snatch a whole new wire harness to just replace the whole mess at this point.
Thanks in advance if anyone has any other ideas.

 

[abcducati]

UPDATE #2: New (old) problem solved, and it was a totally newbie mistake on my part. So I retraced my steps in fixing the issue the last time I worked on it, which led me back to the fuse box and low and behold, the brake fuse was blown (it hadn't been before,). For now, everything is working as it should, but the black scorching around the plastic of the junction between the two wires to the brake switch is still puzzling. If the problem re-occurs, I will further update on the progress. Thanks hivemind!