To test Isolator.
Use a good meter with a diode setting.
Remove wires from center and one side (or both sides).
Touch test probes to center and one side.
One-way is red probe on center & black probe on side. Other-way is red on side & black on center.
Then repeat test with probes to center and other side of isolator.
If isolator is ok,
Probes one-way (called forward bias) will typically read between 400 & 1000.
with probes the other-way, meter will read "1"
If isolater is bad,
Shorted side will indicate near "0" and there will be continuity.
Open side will read "1" with probes either way.
Very true, but for a basic "does it work or not" test, you don't need to remove the wires. Let the batteries rest for a while without any charging from either the inverter/charger or the engine alternator, then measure the voltages at the chassis battery terminal and at the house battery terminal. Turn on the house battery charger, and the house battery voltage should rise but the chassis battery voltage remain unchanged. Then turn of the charger, find the rest voltages again, and start the engine -- now the chassis battery voltage should rise but the house battery voltage remain unchanged.
I don't think this statement is correct since the alternator charges both the chassis and house batteries through the isolator. That is why the isolator is there. Voltage should rise on both batteries.
But... Remember that the chassis battery gets a 'direct feed' from the alternator while the house battery bank feed gets a half volt less due to the diode drop across the isolator.
Gee, on my isolator, it has the same diode reading on BOTH sides, so both chassis and house batteries get the same voltage charge. Why I raised the voltage on the belt driven alternator.
On my setup, I get a higher volt reading on the alternator terminal than either chassis or house side.
Both chassis and house side read real close the same.