1974 911 Turn signal indicator problem.
 

1974 911. I have a problem with the turn signal indicator arrows on the tach, both blink at the same time when I activate the turn signal to the right or the left direction. The turn signal lights on the outside of the car work fine as do all other lighting. I do have a fiberglass front bumper and I replaced the 1974 headlite switch with a 1973 911 light switch.
Where can I get a wiring diagram for a 1974 911?

You have a bad ground on one of the front turn signal housings. I have a 1973 911 which experienced the same problem after I had the car repainted. I recalled that I added an extra wire to the ground in the housing and went to the body. Good Luck!