The GT6’S first MOT test after its lengthy body surgery resulted in a few advisories: a slight imbalance on the rear brakes, a ‘light misting of oil’ on a rear shock absorber and low brightness from the brake lights. The rear brakes were fixed by freeing off the sliding slave cylinders and lightly sanding the brake shoes, then I fitted a new pair of GAZ dampers.
I double-checked the brake light wiring to make sure the stop light and side light connections hadn’t been reversed. These were fine. Out came the multimeter showing mere eight volts at the bulbs, explaining the poor light output.
The GT6 has a night dimming relay, reducing brightness after dark. Clever idea, until it goes wrong. The voltage drop at the brake lights was due to the heavy current drawn by the 21-watt bulbs. A set of Halfords LED stop/tail light bulbs which use mere milliamps avoided the voltage drop and are so bright they can’t be ignored.
LED bulbs resolved the brake light issue.