1987 Thunderbird Brake lights

Like my 88, your Bird has 7 lights. 1 high-mount in the back window, and 6 down below. With the light switch on, the lower 6 should be on, in the "dim" mode. Activating the "hazard" switch should flash the outer 2 on each side brighter, plus the outer front lights. If they all flash normally, then the bulbs and wiring are okay.

If they still don't work, stick your head under the dash and look for the brake light switch, just above and attached to the brake pedal. Occasionally the switch may go bad, the plug may come loose or melt, and more likely one or more of the wires to the switch has broken, since they flex every time you step on the brakes, and nothing lasts forever.

If your voltmeter and test lights show all those parts are good, the next likely suspect is the "hazard" part of the multi-function turn/hazard/dimmer switch.