Dick,
First thing to do from a safety standpoint is to install an AC circuit
breaker between your shore power input and the inverter.
Second. Have you checked the "charged voltage" setting on the Link 2000
panel? It should be set to 13.5 V (default value). If it is set higher,
the charger might be sensing that the battery is not completely charged
and try to continuously start the charge cycle.
Have you tried setting the Link 2000 to the default settings?
Have you disconnected the phone cable from the inverter and tried to
operate it without the Link 2000?

Kelton
s/v Isle Escape

Dick Locke wrote:
Still finding surprises on a used boat.

It has a Freedom 25 Charger/Inverter, controlled by a Link 2000.

When I turn off the charger using the button on the Link, the charger
only stays off for a few minutes. When the fully charged battery drops
to about 13.6v, the charger switches back on. It's subtle, because the
"charge", "accept" and "float" lights and the "charge" light do not
light. If you're not watching the voltmeter, you won't notice.

Is this the way it's supposed to work? The manuals imply that this is
the default option that can be overridden by DIP switches on a manual
control panel that I think the Link replaced.

The only way I can shut down the charging is to kill the 110 to the
Heart. Unfortunately there is no separate breaker on that line.