groundhogy wrote:
Brake controller removal did not change anything.
CLUE: So I pulled the tail light and had the bulb out to observe.
It is a dual filament bulb. Top filament for blinkers and stop. Bottom filament for nighttime tail lights.
When you turn on the turn signal the blinker speed is normal, you correctly see the top filament blinking.
But then you see the bottom filament start to light up . And the blink speed goes up.
I would suggest there is a very small contact between the positive side of the brake/signal bulb and running light. Just barely enough power getting to the bottom filament to cause havoc. Corrosion may play a part in this too, something on the back of where the bulbs are inserted.
Way back on my 94 GM, the brass buss ground bar(neg)on the backside of the rear lamp assembly was so corroded I had to solder a wire across the terminals.
