Directionals on the dashboard...
 

When I use my turn signals in my '70 911, they flash OK on the outside. On the inside of the car, after 2 or 3 flashes, instead of just the left or right directional lighting up, they both light up. Surely someone else must have had this problem at some point. What causes it and how do I fix it?

Mine do EXACTLY the same thing!!!

But I have no idea why.....

I hope we can find out!

I had a similar problem:

Both of the direction indicators in the tach were lit while driving.
Only when I used the turnsignal the interior indicators worked as they were supposed to.

I did some upgrades to my fusebox, and the problem went away.
So my advise is to start by checking all the connections to the fuses. It could also be that the lights in the tach are not properly grounded.

Do yourself a favor and spend an afternoon cleaning all the grounds you can find. Especially the one's behind the parking/turnsignal enclosures, (rain. dirt and other road trash leads to corrosion of these grounds), the transmission strap (the source of MANY electrical related problems) and the starter ground. You should also clean all the bulb socket connections and the 14 pin connector in the engine compartment. Finally, clean all the fuse connections. I think you'll see a great improvement after this. 911 electrical problems are very often ground related. Hope this helps. P.S. there are lots of posts about this same problem. Try a search like "turn signal and ground." Good luck :)

Try a new flasher relay too.

Thanks for the ideas. I'll try them when my other vehicles aren't consuming all of my attention. ;)