Faulty brake light switch?

[Ryan_M]

I am rigging up all my wiring, lights, and new turn signal. Everything works as it should except for the brake lights. They are always "ON". �I believe the problem lies in the brake light switch attached to the front of the master cylinder. I disconnected both wires from it and the brake lights shut off. I put a meter to both points on the switch and always have continuity, even when there is no pressure on the brake pedal. I adjusted the pedal free play all the way out and still have the same result.

The MC, switch, all wires, lights, everything here is new within the past year and have had no real use until just this week. I've read that a lot of the brake light switches are junk right out of the box. When they fail, do the lights stay on or do they not work at all? Is there something I'm not doing that would relieve constant pressure to the switch? I bled the brakes last week too for really the first time but I'm not confident I did it correctly. Would that have any impact on what's happening with the brake light switch?

[F Bill]

If you remove the switch from your master cylinder and check continuity again that will answer whether it is a switch issue or a bleeding one. Chances are the switch is bad unless you are also having bleeding problems.

[Ryan_M]

I just removed the switch and confirmed that it is faulty. I thought I had replaced it when I replaced the MC but apparently I did not as the switch appears to be quite old.  Looks like NAPA carries a suitable replacement so I should be back in business shortly.

[johnrb3b]

Another issue with some of the currently available switches.
Two or three guys on the 3B forum got switches that literally broke apart under pressure from the brake fluid and spilled fluid out through the broken switch body resulting in no brakes.  

If you've bought a new switch, test it in the vehicle in a safe place where you can stomp the brakes and have lots of room to coast if the switch blows up. Or test it in the garage by just stomping the pedal several times to see if you can pop the switch. In the above cases, the switch broke fairly quickly.

[Ryan_M]

NAPA had a similar-enough-to-make-it work switch that I installed yesterday and I now have functioning brake lights. It was worth spending the 10 bucks and extra time jury-rigging the wires just to confirm that there were no other problems. Brake lights were also the last thing standing between me and a real test drive so there was added incentive to find a quick fix. Since I just placed a Walck's order for those head-bolt studs (see my other recent post) I also ordered the correct switch and new copper washers for a better seal at the y-fitting.