There have been several posts recently concerning the operation of the various switches connecting the batteries to the electrical panel on a P42 or 430. I think they are similar. The file is about 350k and only shows the positive leads. This is the diagram of my P42 which is equipped with a generator. The only change from stock is the buss bar where the alternator output connects with the starters and windlass. This was done on the starter solenoid post at the factory but when I installed the Balmar alt. I increased the size of the wiring, hence the buss bar.

1. The round switch labeled inverter draw selector determines which of the two, in my case, 8d batteries the inverter will draw from. I also determines which of the two will receive charging from the Heart when at shore or if a genset is running. I think it is best to leave it set to both but thats my opinion.

2. The two toggle switches next to the round switch control which of the two 8d get to the electrical panel. At this point they are not yet in parallel. They get paralleled at the toggles on the electrical panel. These switches in conjunction could allow one to feed his 12v needs off one 8d while feeding the inverter off the other. Im not sure why there are two switches on the panel.

3. The heart has access to the start battery via the isolator. Since the heart is not normally being used while the engine is running, the isolator keeps the start battery separate from the house.

4. When the engine is running, the isolator is bypassed by the solenoid allowing the alternator output direct access to both the start battery and via the solenoid to the house battery. This prevents the .5v loss to the house bank if it was passing through a diode in an isolator.

5. The diagram also shows that the bilge pump can access all house and start batteries via its connection to the start battery switch B terminal and hence the house bank via the isolator. It also shows that the starter can get voltage from the house battery.

97 P42(430?) wiring diagram