acc7484 52 #1 Posted March 11, 2021 Hello all, Wheel Horse 1988 520-H model 31-20OE01 I just received a new Tach ( from a Marine Surplus in the mail today. However There are no instructions with it. There are S G I designations on it . on the old Tach Can someone please verify the correct hook up. Thank you Share this post Link to post Share on other sites
Handy Don 12,674 #2 Posted March 11, 2021 Sensor, Ignition, Ground. Sensor is from the stator (sends pulses of electricity to the meter) Ignition powers the instrument Ground is, well, ground. On the original, Pinks are Ignition and blacks are ground and blue is sensor Hoping the specs are for an engine with the same number of pulses per revolution as you engine (the Onan has 9 pulses per rev). Share this post Link to post Share on other sites
Handy Don 12,674 #3 Posted March 11, 2021 Looks like there were two grounds on the original. Test with ohmmeter for conductivity between the GND and the terminal below it that had the blacks connected. Share this post Link to post Share on other sites
acc7484 52 #4 Posted March 11, 2021 The ground on the old unit is the upper left terminal...that has no connection. So it appears there is an internal gnd . OK ....thank you Don .... Share this post Link to post Share on other sites
