I'll check that tomorrow. I am going to call BlueSea to see if there is anything in the ACR that might prohibit full charging voltage from going thru the ACR. I checked the input line to the second battery (from ACR) and it seemed to have more voltage than the battery (12.9-13.0v) but less than the line going from the primary battery to ACR which had 13.8v.
Thanks
Well, testing with a multimeter can sometimes be a bit deceptive. Basically, when you test with a meter, you are creating and testing a "short" circuit. Not a "dead short", but a circuit that is not the same exact length as whatever it is you are trying to troubleshoot.
So the voltage measured on a "long" circuit - say from the alternator through a wire to the chassis battery, and then through another wire to the ACR terminal, and then through your meter, and then to whatever ground you are using, and then back to the alternator - can (and often will) read a different number than the voltage reading from a "short" circuit, such as battery + through the meter and back to battery -.
But conversely, even if the one circuit is "longer" it can also have a lower resistance - which will allow the meter to read a higher voltage. Since the battery is one big resistor, you can see a lower voltage measuring across its terminals than you might see measuring the voltage at some other point on the "charging loop".
That's why I suggested A) making sure that both batteries really are charged, B) giving the vehicle charging system enough run-time to make sure that both batteries have had time to be topped off to whatever the voltage regulator is holding the "12v bus" at, and then C) measuring both batteries. They should be equal and both equal to the voltage that the voltage regulator is holding the bus at.
If they are, the ACR is working.
Even if one battery is a bit worn out, it should still come up to a surface charge equal to the bus voltage. It just won't stay there long after you remove the supply voltage that holds it there.
Now, the ACR is just a solenoid - a switch with the contacts pulled into position by an electromagnet. An electrician would call it a contactor or a relay. The contacts inside that connect the two large terminals can get damaged or worn out - like the points in an engine ignition system.
The same sort of gizmo used in electrical work:
Is usually designed to be rebuilt. The rebuild kit usually includes new contacts, and sometimes new springs and screws and whatnot:
You can't (or probably can't anyway) rebuild your ACR solenoid.
BUT - even if the contacts are worn or burnt - it ANY power is getting through it, given enough time, the second battery should eventually reach parity with the bus voltage. It'll just take longer to get there.