Bought my Fourth car yesterday! 1947 Oldsmobile series 76 fastback

[init4fun]

Originally Posted by Electronic M

So I installed the relay and the old switch behaved it's self for about a day before coming on by itself and sticking. So I installed the new stoplight switch and went for a test drive and after a few blocks the stoplight relay started chattering at triple the rate of the turn signal flasher. A quick stomp of the brake pedal stopped the chatter but it comes back periodically...It will still also stick down.

There's ~1/8" of play in the pedal when released and jiggling it within that will click it on and off... I'm not sure if the switch is too sensitive or if the master cylinder has some problem.
The 2 switches were both napa cheapies. I'm thinking about trying an autozone part to see if a different source fixes it.

Wow that sucks . I'm curious , does your car have the brake light switch mechanically linked to the pedal or is it a pressure activated switch plumbed into the brake lines or master cylinder ? The one I had the problem with was the pressure switch kind and with slight applications of the brakes the switch wasn't fully closed and the brake light would flicker , when I put the relay in I put in with a brand new switch that hadn't been permitted to arc across it's contacts and the relay action was smooth with no chattering .