Originally Posted by BobTurner
It gets its data from an external linear resistor; data goes into one of the Aux inputs on the EFIS. EIS not involved. Depending on how the linear resistor is wired (does it get power directly?) you may have to activate a bias resistor in the EFIS set up.
FYI The flap position indication gets the travel data from an external linear resistor, usually a POS-12, I think (Assuming the Ray Allen servos are used.); however, the trim system indicator information is created by the trim servo itself, not a separate unit. (Through the Green, Orange and Blue wires. The two white wires actually power the servo motor and go directly to the switch/ relay.)
Anyway, assuming that your wiring is correct, since you said it has been working all along, we could assume the problem was likely caused when you had the EFIS and EIS out.
I would first look closely at the connectors and see if a pin has been pushed back/out, a pin bent or broken off, or if a wire has been cut or pulled loose. Look at the EIS connector as well as the EFIS connector, particularly the serial wire pins and the Serial port pins you are using for the trim system. Also inspect the wires themselves for cuts or abrasions.
If that doesn't work, I would verify that the programming in the EFIS/EIS didn't get changed accidentally.
If the trim system is actually working, but no indicator on the EFIS for both pitch and roll, when you used to have it, I think that pretty much narrows it down to wiring at the EIS/EFIS or programming. Especially since it happened right after you worked on it.