I want to find out why the trim indicator on my digital tach stays at the medium position. First, I'd like to see if the sender unit is any good. There are three wires leaving the sender: Black, orange, and pink. What type of device is this, a variable resistor for instance? I can unplug the sender and isolate it from the rest of the wiring. Can a volt-ohm meter be used to diagnose this? The orange lead on the tach side shows 5VDC when the key is on.
