Re: Beta Marine BD722 Tach kicks in after I enable extractor fan!
It's likely that the alternator is providing the (RPM) signal to the tach. If your batteries are all charged up and there is no other load on the alternator, the alternator regulator removes the field from the alternator. No field, no tach signal. As soon as you add a load, alternator is back on and the tach then works. Just a theory. Will switching on any other load make the tach operate? (Say, the fresh water pump?)