For as long as I’ve owned my ‘66 98, I’ve had to pay attention to keeping the tail lights working properly. They’re complex: 4 reverse bulbs, 4 semi-dim driving bulbs, left turn/brake, and right turn/brake. I use 2357 bulbs (extra bright motorcycle bulbs) for my turn/brake lights. They have shorter lives than the factory 1157, but burn brighter. I live with the trade off.

Along the way I’ve replaced bulb sockets with junky latter day aftermarket sockets, then back to used GM again for better quality. I’ve rebuilt the entire rear harnesses with fresh wire, and I stay on top of the bulb filaments. A good multimeter and wiring diagram goes a long way to help find problems.

Tonight I found something sort of new. I just wanted to put it out there as noteworthy. What’s below should apply to most all GM’s with the 2 pin brake light switches from the mid-60s on until maybe the 80’s, or maybe beyond.

GM brake light (and cruise control) switches are simple 2 pin spring loaded devices. When the spring extends, the contact is made and the brake lights glow. If contact is bad, sometimes only one side or the other will glow, making you think it’s a bulb. But sometimes it’s not.

I unit tested my brake light switch with my multimeter using the sound function. It was fine. I tested the bulbs and wiring to the trunk with a simple jumper wire to simulate an activated switch. That was fine too. But why didn’t they work together as designed???

What worked tonight to fix things was pop the female terminals and restore the tension they had in their plastic shell so they don’t move when you connect the male side. Then I squeezed the male terminals on the switch side together just a bit - not apart like you might think would improve connection tension - together -. Squeezing the male terminals together just a few degrees got both brake lights back.

Nice little project. Hope this helps those of you who’ve struggled with brake lights along the way.

Chris