Left turn signals quit when braking

[biggus]

My 77 M880 has an electrical issue. All lights abd signals work but when I hit the brakes, the left turn signal (front & back) stop blinking when the brake lights come on.
Any help appreciated.

 

[Bob H]

Ground related.

 

[biggus]

Any tips on where to start looking?

 

[fallen]

I have heard that a filament from a two filament brake light could have an internal short and cause the signals to flash when the braked are applied. It could be some thing related. I would replace the bulbs and see what happens. It could be as easy as swapping left and right side bulbs and seeing what happens.

 

[MatthewH]

Get new bulbs. If they are cheap dual filiment, or are a single filiment, that will cause this problem.

Also check the grounds, like Bob H suggested. If all else fails, clean them really good and grease afterwards.