Battery Isolator Malfunction

CA Traveler wrote:
I have the Intellitec Big Boy solenoid and a BIRD Diesel controller which is the battery isolator.

Yesterday on shore power the house battery was being charged and the chassis battery needed to be charged (12.5V) but the solenoid was not connecting the two battery posts.

The solenoid was humming and the coil voltage was about 4V. My understanding is that this is normal after the initial 12V pulse to engage this latching solenoid.

With further testing in mind for this morning, it’s now working and charging the chassis battery. I now suspect that the solenoid operation is intermittent and it needs to be replaced.

Anyone else seen this or have any suggestions?

First off, the Big Boy Isolator solenoid is NOT a latching solenoid, It requires sufficient voltage across the coil to remain closed.

I suspect you are right in thinking that the solenoid is failing. Probably due to the constant coil heat, but that 4V sounds a little low from my experience and could be an indication that the Bird circuitry is beginning to fail. Typically, the bird output only drops to about 8-9 volts.

I would replace the solenoid before it ruins the Bird.