There is a small plastic case where the tachometer brown wire terminates. Full circuit ID starts with wire diameter, .8 (mm), then color (BRN) hyphen then circuit ID (104) and finally insulation type (SXL). SXL is thick wall polyethylene. Wire diagram descriptors are on chapter 2-2 of the TM.
If using Appendix E-11 from TM 9-2320-289-34, circuit is 104 starting from left (that is port for the Navy inhibited
) alternator. Wire diagram shows it transiting the firewall bulkhead 3rd position from the right.
In the cab, wire color is still brown and ID still 104. It terminates at the tach buffer module. The buffer module has 7 wires, brown, 2 black, dark green, light green and tan. Tap into the brown for alternator AC to tach.
I've tried all sockets on the STE-ICE port with my frequency meter, nothing. Sockets leading to the tach buffer module are D (purple 857), multiple grounds and C (green 85
.
Tach buffer module is smaller than the glow plug controller, also hanging from harness and near the STE-ICE port.