512TR Intermittent Brake Lights

what will happen if you push the brake pedal slowly and keep it pressed a while?

 

My brake light switch failed twice. Need new one

 

take an ohmmeter and meassure if the switch will work. I think this switch is the problem.
down at the pedal there it is, easy to test but not so easy to reach
it is plastic and when you push fast the pedal the spring in the switch is strong to close the switch, but when you push slow the spring is not so strong to close the switch ( only my thinking).

 

Your 512TR brake light switch is designed like most other brake light switches where the mechanical action is sort of backwards -- when you step on the pedal, the plunger of the switch extends out to close the contacts (it doesn't get pushed in), and has nothing to do with how hard you are pressing the brake pedal:

When you do a fast tap = the force closing the brake switch contacts is the spring force inside the switch + the inertia of the plunger rapidly moving and then getting stopped quickly (and may actually change which locations on the contacts that are making contact).

When you press slowly = the force on the switch contacts is just the spring force inside the switch (and since this is the normal operation, the locations on the contacts that are making contact will be very repeatable and have a lot of cycles on them -- and the current to run the brake lights is surprising high, like 8~10A, so that's a hard life on the contacts and burns/oxidizes them).

Your symptom is a bad sign for the the brake light switch itself, but, as the others have said, you should make some electrical measurements to really confirm/deny: With the key "on", one of the terminals should always be +12V relative to ground. The other terminal should be +12V whenever the brake pedal is pressed. If this other terminal is +12V relative to ground when you do a fast tap, but not +12V relative to ground when pressed slowly = you can replace the brake light switch with confidence (although your brake lights are effectively a volt meter, and are already telling you this ).

 

FWIW, I had a bad ground on my rear stop lamp assembly on the passenger side. What would happen is the turn signal lamps in the gauge cluster would come on dimly when I hit the brakes. The system needed a ground and was going through that way to get it. I repaired the ground, cleaned up the contacts in the brake switch and solved my issue. Just a heads up to look at those connectors as well. Ohmmeter wouldn't tell you much, more like watching a voltage drop across there would reveal any issue (probably can see if the lights are just dim overall and find whether there is a ground issue or not)

 

great, so 1 problem less