Welcome to the dead Volvo
hour meter club. Ours are also dead, but once in a while they kick back in. Sometimes they just display garbage. It isn't related to the external regulator
because ours are stock alternators and others on other makes of boats have this problem also. I have tried cleaning
contacts, checking wires for impedance, etc, to no avail. It is a Volvo
design problem that can be fixed only with $$$ by buying
new tachs. And even then, you will run into the problem again down the road, because Volvo has not redesigned them.
However, the only non-esthetic purpose of the meters is to keep track of the engine
hours over longish periods of time for maintenance
reasons. So why not simply install dedicated hour meters across the alternator
outputs and leave them in the engine compartment? I got a nice, small digital hour meter at Graingers for $25 that I use to monitor
the reefer run times. When we get back to the States, I plan to install these on our engines.
Hope you are enjoying your boat,