Brake lights out- 84 240 DL wagon

The switch under the pedal should have power at one wire with the brake pedal up, then power at both wires with the pedal depressed. After leaving the switch, power goes to the bulb failure relay, a cylinder (probably black on your car) clipped to the lower dash frame beside the steering column. The wire from the brake light switch goes to the terminal marked "54", the wires to each brake light come from the terminals marked "54L" and "54R". Often the brake light circuit inside this relay has a bad solder joint. You can change the relay, or if handy with a soldering iron, fix it. If you're shopping used, note that the relay from the later cars with a 3rd brake light (1986 and newer) will cause the bulb failure light to be on all the time the brakes are.

I've seen this happen when solder joints cracked in the bulb failure sensor.