Hi I have a 66 that when the left directional is on the right rear blinks, and when I turn the headlights on the right directionals work but not the left, I cleaned up the connections, and replaced the switch in the steering colum, and lights are bright so it doesn t seem to be bad grounds, any ideas ?

 

May be in the column or a crossed wire. The easist first step is again to check the grounds. Only takes a minute.

 

To agree with 67. Bad grounds on the light sockets will drive you crazy. If you have the wiring in the correct spot,clean the grounds (not just check them)