Tacho Problems

[Nissan cedric]

Hello to all ... It appears the tacho is in need of some TLC.

When traveling along the highway my tacho will suddenly.
have a fit and drop to zero then up again to 2000k then back and forth eventually up to the original reading it will do the off and on for seceralmminutes, when it then return to normal steady reading. This event also occurs operating off road. Any suggestions re cause and how to fix. Ta in anticipation. Nissan cedric

[mudnut]

G'day, Nc. The tacho signal comes from the coil (Blue Wire), to a Tan coloured resistor taped or cable tied on or near the top radiator hose. The wire from the resistor to the tacho is a Yellow wire with a black stripe.

Check all of the wires and connectors in the harness from the coil, up to the gauge cluster.

Failing that, pull the cluster out. Check the screws are tight on the back of the tacho and that the copper conductor sandwiched in the plastic from the loom connector to the tacho is intact.

Visually check all off the solder joints on the tacho printed circuit board and that there are no problems with the legs of the components.

The orange arrows should show the tacho signal input and the Yellow black wire. (disregard the yellow arrow and circle).