The resistance should be low in one direction and high in the other. A battery isolator typically is used in situations where multiple batteries are required and its primary purpose is to ensure that the failure of a single battery will not incapacitate an entire electrical system.

Cooper Bussmann 240 Amp Battery Isolator With Wiring Kit
How to test a battery isolator. Don if its a diode isolator you test it with an ohmmeter with no battery connected. Diode versus solenoid battery isolators. There are two main types of. A battery isolator is a one way electrical battery that allows an electrical current to flow in one direction but not the other. To find out if the isolator is sending charging current to your batteries start your engine and check the voltage at the center post that comes from the alternator. The idle batteries are charged by the alternator and the battery isolator can switch power sources if the battery in use suddenly fails.
You should have one high and one low resistance reading. Follow the wires attached to the battery isolator and make a note of which terminal is attached to the chassis battery the coach battery and the alternator. Put your meter on the 20 volt dc setting. Step 2 check that terminal one is wired to the coach battery and confirm with your operators manual that this is correct. Connect the leads take a reading reverse the leads take a reading. The battery isolator uses sensors to determine the number of batteries it is connected to and to draw power from the strongest battery.