[Richard]

Ok, thanks for the readings. What does NA mean? No voltage at all? or batteries not connected? or something else?

By charger, I mean the coach charger, the Heart.

With charger off, measure the voltage on the test battery. Now turn the charger on, the voltage will go up if the charger is working. Measure the voltage on the batteries, not the Link 2000 panel.

E10 is an error code saying the remote is seeing low voltage.

The shunt wire thing is not a valid theory.

Interesting that the set of batteries behind the tag tire is charged.

Didn't you just have new batteries installed before you went out to Tom's. The installer may have wired them incorrectly.

On your Link 2000 panel, you should have Bank 1 and Bank 2. As it came from the factory Bank 2 is the CHASSIS battery, not the two behind the tag tire. But that was 20 years ago, and who knows how it is wired now.

Minus amps on the panel would indicate the charger is not charging.

Starting at the inverter connection for the battery cables, it would help for you to trace those cables and make a sketch.

Forget about load testing for right now, voltages are good enough. With those voltages so varied in your house bank of batteries, I suspect a fundamental wiring problem. It looks like the charger is charging batteries 3 and 4 in House Bank 1, but those batteries are not supply voltage to the coach. And it looks like the charger is not charging batteries in House Bank 2 but they are supplying voltage to the coach.

Don't forget to turn the merge switch to off.