bad turn signal switch?

[SkidMark]

Getting closer to firing my son's '65 fastback.....finished the wiring last night. Interior lights work, tailights work, brake lights work. However, if I hit the brake lights while the tailights are on, the left light goes completely out, right one works fine. Turn signals dont work at all. Midlife restored my under dash harness and tailight harness, so I'm confident the wiring is good. My dimmer switch is new also. About the only thing thats not new is the turn signal switch. Any way to test it?

 

[B67FSTB]

Make sure the ground straps or pigtail are grounded to the chassis firmly/good contact.
A bad ground can do weird things with the electrical system of your car.
Make sure the rear taillight buckets are grounded.
my 0.02 eurocent

 

[apollard]

Bruno is correct - you most likely have a bad ground check them all - turn signals, tails, everything. There is a ground for the front TS that can break in the harness near the rad. support, which causes what you describe. BTDT