Originally Posted by ronald.saumure
I am looking for the isolator that the alernator uses to select what battery it will charge.
On the Sunseeker and Forester, the "Bi-directional Relay Delay" doesn't decide which battery to charge. It decides when to energize the relay that connects the chassis 12 volt system to the coach 12 volt system. It will connect the two systems when:
1. The convertor brings the coach system voltage high enough (in effect, there is enough extra 12 volt power to run the coach, charge the coach batteries, and charge the chassis battery at the same time),
2. The chassis alternator brings the chassis voltage high enough (as above, but in reverse),
3. Or, the driver engages the emergency start switch. This engages the relay and connects the two systems so the coach batteries can be used to boost the chassis battery to start the engine.
You can hear the relay when it is energized if there isn't too much noise. It's located behind a small panel on the left side of the lower step.
If the BIRD senses that connecting the two systems lowers the voltage too much, it will cycle the relay on and off every few minutes to avoid running down the batteries in the coach or chassis.