Tach / Battery Charger

[allsail68]

On owners forum an issue was raised re our tach's pegging out and then going to zero while running the motor with the battery charger on. There were comments that running the engine with the charger on was not good for the alternator and could be causing the tach to malfunction.

This was the first time i heard of this although my tach has done the same thing but also has done it while motoring away from the dock. After an initial occurrence or two it settles back down reads fine after that.

My assumption was i need to check my connections, get a new tach, etc. The engine make would be either Universal 35 or Yanmar on our sailboats of recent vintage.

Our's is a small forum and i know there is a lot more expertise and experience here.

Thanks.

[donradcliffe]

Most tachs are fed by the unrectified alternator output, and if the battery voltage rises above the alternator regulator setpoint (like if you were running a separate battery charger) it will turn off the alternator, making the tach stop working. The three stage regulators will sometimes also turn off the alternator/tach for a few seconds as they switch from the acceptance (higher voltage) stage to the float (lower voltage) stage. It's a normal function, and running the charger won't hurt the alternator.

[neilpride]

I have the same problem the other day when motoring along Dominica coast, my perkins tach stop working and the alternator output stop working, i have 2 alternators, 1 is a balmar hig output alternator with a 3 stages balmar regulator , and after investigate the problem i find the Airx windgenerator regulator interact with the engine regulator, solution::: stop the wind generator and the tach back to life, also be sure that the batery swicht is in good condition , sometimes when swicht from battery 1 to both or 2 there is a false contact in the swicht. Cheers.