Retiredvette52

Brake lights stopped working and I suspect the switch. I have voltage to the switch on one terminal and nothing coming out when the switch is closed or in other words the brake pedal is depressed. When eliminating the switch and crossing both wires I have brake lights. Dazed and confused with continuity check of brake light switch operation and operation when voltage is applied. Bench test of switch with a multimeter on ohm setting reveals open circuit with the switch fully depressed and a closed circuit when switch plunger is released. Switch works with resistance but not voltage??? I suspect a bad switch but lost as to why the switch appears to check out ok with resistance but won't pass voltage. Any thoughts?

65GGvert

In your scenario, the only thing that makes sense to me is that the internal contact is corroded enough to stop the voltage, but will still read resistance. As long as the switch is springing out to close the contacts when the pedal is depressed, it should be ok. One outside possibility is that you are losing connection with the wire connector itself and not switch leg. If you have 12v on the (orange) wire coming in, but not on the (white) wire coming out, there's no doubt it's the switch or the wire connection.

Retiredvette52

I bought a new switch, connected it and the switch works properly along with the brake light activating and deactivating. Curious, I took the bad one apart and could see that the contacts were not meeting flush when activated...they were just barely touching and I assume this is why I got a resistance measurement but too poor a contact to pass proper voltage. Apparently it doesn't take much to knock these switch plunger contacts out of whack. I'll crawl back in there tomorrow to install and adjust.

alexandervdr

Are you sure the switch 'top' can move freely when mounted?

Retiredvette52

Thanks for the follow up. Beyond the continuity and voltage issue, I have since replaced the switch and lights are now working properly. Apparently some of the switch plungers open the circuit when very close to the plunger housing, less than an 1/8". Problem with such a short activation between open and closed circuit is you don't have a lot to adjust before the circuit closes, when plunger extends further from the housing allowing the brake lights to activate. With some tweaking to brake light switch bracket I was able to find the perfect spot for the circuit to close and open consistently w/o the brake pedal bottoming out against the brake light switch housing. Replacement switch operation varies from one to another, at least that's what I found.