Brake Light Switch Test

NOTE: Perform this test when brake pedal actuation does not disengage speed control system. On vehicles with M/T, ensure that clutch switch is working properly before performing this test.

Check for stoplight operation with maximum brake pedal effort of 6 lbs. Check brake pedal actuation and stoplight switch if pedal effort required is excessive.
If stop lights operate correctly, check for battery voltage on circuit No. 296 (White/Purple wire) of amplifier 6-pin connector. Activate brake lights, check for battery voltage on circuit No. 810 (Red/Black wire) on "E" Series, circuit No. 511A (Light Green wire) on Bronco and "F" Series and circuit No. 511B (Light Green wire) on Aerostar, Bronco II and Ranger.
The difference between voltage readings should not exceed 1.5 volts. If difference is more than 1.5 volts, check circuit to find source of high resistance. If brake lights do not operate, check brake light switch for continuity, fuse, bulbs and wiring.