Hi, I am not familiar with your coach but it seems from previous postings that you have the Bird battery charge monitor system and you are still not getting the alternator charging the coach batteries. A generic Bird schematic is attached for a basic reference....but your actual coach wiring may be different.
You mentioned that your husband measures 14 VDC when the engine/alternator is running (I assume measured on the chassis (engine) battery), but only 12.8 VDC on the chassis battery at the same time. I believe the Bird sensing unit waits 2-3 minutes after sensing 13.1 volts before closing the isolator relay to connect chassis and coach batteries together. Do you have an emergency battery start switch at the driver location ? If yes, with engine running, when the emergency switch is operated, do you hear a relay operate and does the coach battery see the alternator charge voltage at that time?
Basically this is manually operating the Bird system “isolator” relay (connects chassis and coach batteries together while emergency switch is held operated) in case the Bird voltage sense unit has failed. If your coach batteries see alternator charge voltages now (or closer values) when emergency switch is operated, then the isolator relay is likely good. Some isolator relays also have 5 amp fuses mounted on the relay for control wiring so check them if equipped. It is possible that the Bird monitor box has failed; wiring issue; bad connection etc.
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