Alternator repaired, now tach not working

[Coriolisbc]

Hi All;
Recently my tach slowly quit working, then I noticed that the Voltmeter went below 12 V while the engine was running, and the Battery Charger amps went way up when I hooked up to shore power after motoring for awhile.
I replaced the alternator, the Voltmeter is up, but the Tach is not working.
Suggestions?

 

[Maine Sail]

Hi All;
Recently my tach slowly quit working, then I noticed that the Voltmeter went below 12 V while the engine was running, and the Battery Charger amps went way up when I hooked up to shore power after motoring for awhile.
I replaced the alternator, the Voltmeter is up, but the Tach is not working.
Suggestions?

Test the continuity of the tach wire at the back of the alt and at the back of the tach. If you have continuity this is good. Now run the alt and set your DVM to DC volts and test the "AC Tap" or stator terminal on the back of the alt. You should see roughly half the volts you see on the B+ alternator output stud or somewhere between 6V - 9V.

If you have half the volts on the AC tap and continuity on the wire then it points to a bad tach or you reconnected to the wrong terminal. Normally if the alt is putting out current the AC tap / stator tap is working.

I suspect you reconnected to the wrong terminal or your replacement alt does not have a stator tap for driving a tach...?

 

[Coriolisbc]

Thanks Maine Sail, will do that tomorrow
CBC

 

[Coriolisbc]

Back on boat stator terminal reads 14 volts
Checked continuity ok,
Tach still not working