Any ideas?

 

I had that same problem with my tach. not working. I suspected bad trailing coils, but it turned out the MSD boxes, that were hooked up to the trailings, were bad. However, I've driven the car for about a thousand miles (more like autocrossed, road raced, etc.) with the MSD's not working (this was before I figured they were bad). My RX ran fine, idled smooth and I'm not sure how much damage I did when I drove the car without trailing spark. (My T1 coil had spark for about 2 seconds at startup and then nothing. I checked my other RX and the trailings are firing all the time when running.) I have since then disconnected the MSD's and tach now works as well as trailings firing all the time when running. (Sorry if I thread jacked.)