I need some help on my brake problem, back story is I’m installing a painless wiring harness for my 1977 Ford F-250 and I pulled in the wires to the brake switch and my brake lights are on and when I click the button they turn off so something is backwards

 

Easy you have the wrong switch, your switch should be a N/O however there is a replacement switch that looks identical that is N/C which is wrong for these trucks. You can verify your switch with a multi meter.

 

oh ok how can I check it with a voltmeter

 

You need a continuity tester, it sounds like. Meter probably has it. It beeps when the circuit closes.

 

No help but how did you wire your horn??? Im 95% finished with my AAW harness. Its GM based and I cant get the horn to work.

 

where can I buy a N/O brake switch I tried to buy one somewhere else and still no fix

 

I replied to your other thread, but the brake light switch should be normally closed NOT normally open. The brake pedal holds the switch button in (which opens the n/c switch and turns off the lights)...as soon as you press the break pedal, the button releases and closed the switch, turning on the brake lights...

 

There are plunger type brake switches that work opposite of each other, and they have different mounting scenarios. One mounts above the pedal and as the plunger extends when you push the pedal down, closes the switch. The other mounts below the pedal and as you push you compress the plunger, turning on the lights. Sounds like you have the latter, but mounted above the pedal, so you just need to find one that works in extension.
If you are buying switches for your truck and they don't match what you have, then either someone in the past changed yours out to a different mounting configuration, or Ford did.
I've seen them both ways and have bought both types of switch.

Definitely post up a pic when you get the chance and we'll compare to what ours look like. But since there are two types, rather than re-orient yours to work with the existing switches, it seems to me it would be better to find one that works the opposite of yours. Even if it happens that you have to source one from a mid-seventies Chevy truck for the parts guys to find the right one.
What is your truck specifically too. Is it a standard or SuperCab? Is it a single or dual rear wheel (did they even make 250 duallies, or was that only for the 350's?), standard rating or Camper Special? Something else odd about yours maybe?
Don't know if any of that would change the pedal configuration, but hey, Ford did some strange "variations on the theme" back then. Didn't know 150's came with leaf springs in front until I saw my first SuperCab. Had only seen once before a dual charcoal canister setup until someone just posted up a few days ago their 350's twin setup. NumberDummy has said many times that there was something like 19 (or 54 or a million!) different brake pedal/booster/master combinations on our trucks!
Maybe one of those included a backwards mounted light switch?

Is there by any chance a second switch for cruise-control that looks the same? If so maybe that's what they're giving you at the counter.

Paul