Help 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 a square moduale Dont know how to test that piece whatever it is.
Any suggestions?

 

[NYBo]

Re: Help Tach wont work

Sounds like a question for the Mercury outboard section.

 

[Barnacle_Bill]

Re: Help Tach wont work

Test your rectifier even tho it appears to be charging.

If you use an analog meter set it on the RX1000 scale.
If using a digital meter, set it on the diode symbol.

1. Disconnect the battery leads.
2. Disconnect all wires on the rectifier.
3. Connect the red test lead to ground and the black lead alternately to terminals A and C.
The meter should show continuity.
4. Connect the black lead to gound and the red lead alternately to terminals A and C.
The meter should not show continuity.
5. Connect the black lead to terminal B and the red lead alternately to terminals A and C.
The meter should show continuity.
6. Connect the red lead to terminal B and the black lead alternately to terminals A and C.
The meter should not show continuity.
7. Replace the rectifier if you do not get correct readings.

 

[jeff6898]

Re: Help Tach wont work

Ended up replacing the rectifier and it now works perfect.