Tach wont work

[jeff6898]

1991 Mercury 90HP
Tack will not work things checked so far

Have power to tach
have good ground
took out tach put in friends boat works perfect
put his tach in my boat does not work.
Have continuity from grey wire from motor to back of tach
Battery is charging great so I am guessing rectifier is good
boat runs and idles perfect
I see the grey wire goes into the voltage regulator
Any Suggestions

 

[BassnKY]

Re: Tach wont work

What is the tach grounded to? have you tried running a temp wire back to the battery? There could be something between where you have it grounded and the battery.

Can you detect any voltage at the gray wire when the engine is running?