Dead Glideslope needle

We've got a dead glideslope needle on our #1 indicator. (KI-209 driven by a
KX155 12v) GS flag works, needle stays centered.

I dug through our log books and noticed that this also happened in 2002 and
was repaired by "repair to aircraft wiring". I contacted the avionics shop
that did the work and they looked up the repair order. They repeated that
the GS needle was inop and the unit bench tested good and that a wiring
repair was done on the aircraft.

I've haven't seen the back side of a 209 or a KX155. The avionics tech that
previously repaired it says " it could be any or all of the 4 wires that
connect the +/- GS flag or the needle"

Can someone explain the wiring?

Thanks,
Jim Burns