There should be only two wire connections on the stop light switch. You need to put a constant 12v supply to one side of the switch and the light wire itself to the other side. The switch then needs to be adjusted so that the brake pedal holds the switch in to keep the lights off. When the pedal is depressed the lights will go on. If they stay on all the time, re-adjust the brake switch.
It is threaded into the master cylinder. If you can't reach from under, remove the fuel tank to expose the master cylinder and brake light switch.
The neutral switch on a 1965 Chevy Impala is located under the transmission shifter. It detects when the vehicle is in park or neutral and allows the engine to be started.
The switch is mounted near the bottom of the steering column under the dash and above the brake pedal on the left side.
Recommend you get a stock signal light switch. This may be your problem.
Kind of vague on the question. If all other rear lights work....tail and turn signals, I'd say it's the brake light switch. You'll find it mounted under the dash, just behind the brake pedal. As you press the brake the switch "opens" to send the signal to the brake lights. These replacement switches are really inexpensive and available at any parts store.
How do I release the frozen brakes on the drum of a 1965 Chevy 3/4 ton pickup
The switch should have a chrome bezel (a big nut) that screw on the front of the switch to hold it to the dashboard. Unscrew this and it will come out from the back. It will have a connector that will unplug from the rear of the switch.
Mind Switch was created in 1965.
Light Sound Diffused - 1965 was released on: USA: 1965