I think I know this guy...
Anyway, for anyone else...
Brake LINE switches are a pain in the butt!
Bad enough when factory installed, keep in mind when they fail you have to open the braking system, bleed EVERYTHING out again,
And if you put one in, make sure the nipple points UP with electrical terminals DOWN.
These things hold air bubbles like they were gold, and you never know when they are going to give that air up into the lines and cause issues.
I would SUGGEST you buy a 'T' fitting that plugs into the master cylinder, then the line screws into it,
With a side port that allows for the switch.
Cutting and flairing a line for the switch, especally on OLD Lines, is virutally impossible to do without having leaks.
Old lines rust, and the rust makes them UNDERSIZE which makes them a pain to clamp for flairing,
Along with rust making them brittle, so they like to crack before you get the inverted flair/double flair done.
Since they are hard and brittle, you have to crank the
out of the threaded brake line nut, into brass, to stop the leaks...
You are just asking for rounded off brake line nuts, stripped brass threads, and siezing problems between threaded pieces.
The other issue is,
Brake lines have back pressure on them.
This is to keep the pistons at the wheel cylinders/calipers in close proximity to the friction surfaces.
If they retracted fully each time you let off the pedal, you would have to pump up the brakes before they worked...
So you have to make darn sure you have the correct switch for the back pressure you have in the lines!
A switch with too low an activation pressure and you will have brake lights on all the time.
A switch to too high an activation pressure and you will have brake lights that don't come on until you hammer the
out of the brake pedal.
This is dangerous since most of us don't hammer the brakes at each stop,
We feather or 'Haze' the brakes to slow down, and the switch doesn't come on and we get run over from behind.
(ask me how I know this... )
There is a reason spare tires and water/fuel cans in the back became so popular in Jeeping when they were originally designed to mount on the side of the vehicle, and I suspect the pressure switches were no small part of it...
These became the original 'Crush Zones' so the guy plowing you in the back didn't immediately get into the passenger compartment!
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LINKAGE SWITCHES come in all shapes, sizes and since you can mount a linkage switch on something fairly flimsy, they are easy to mount...
With a linkage switch your brake light come on IMMEDIATELY when you touch the pedal,
Assuming you have a good return spring on the pedal,
And they keep that soccer mom on the cell phone from ramming you when you are just slowing down and not particularly hammering the brakes for a full/fast stop...
We can't do anything about the soccer moms in minivans & SUV's, but we can give them a little notice with 'Third' brake lights in the spare, some bright tail lights, and early warning and HOPE they are paying enough attention...
I know my spare saved me serious damage at least twice in highway collisions, and saved me minor damage more times than I can count from rear 'Bumps' on the trail when someone couldn't stop in time... Slick Clay Mud or Slick Shale doesn't care what tires you have, sometimes there just isn't any stopping in time!
