Hey there, thanks for your attention regarding my 1968 XR7. I recently bought a solid state turn signal sequencing unit to replace the old analogue one. Everything worked well so I replaced the old incandescent bulbs with new LED ones. Everything worked OK until a few days ago when I noticed that only the center lights flash when the turn signal is used. Should I replace the flasher can in the dashboard or its the problem bigger than that???
Welcome to the insanity Ausgang 
When you get a chance post some pics of your cat, we all like seeing others rides. Don’t know where ya got the solid state unit and led’s but heres a thread all about the new systems, in page 2 is the requirements per year. 
On a 68 (and like wise a 67), the flasher can only causes the dash indicator lights to flash. The fact that you are getting power to the tailights (even though only your center lights are flashing) changing the can will not do anything for your issue. Here are a couple of things to try:
-
When you installed the solid state version, and if you removed the k10 emergency relay, make sure that the spade connector from the new unit is plugged into the K10’s black connector on circuit 514 Blue wire. Retest to see if your issue has been resolved.
-
If #1 doesn’t work, check if there is power on the blue wire when the turn signals are in left/right mode. There should be no power here if you turn on the emergency flashers.
-
If #1 and #2 don’t solve your issue, replace the LEDs with the incandescent bulbs.
BTW, if your old Analog system works, you can run LEDS with this system however you will need to either add a load resistor to the taillights.
Coach Jack