Battery Isolator
 

Hi, i posted awhile back on here about getting a feedback noise on my low air warning buzzer. I was in the midst of trying to figure it out and it stopped.

I am now in the coach on holiday and have been parked for 2 months. The other night it started to buzz again.
I usually turn of the battery disconnect for the chassis batteries when parked. When this buzzing started I noticed that there was power to the ignition that should not be there unless the battery disconnect is turned on. I also have a Lambert battery maintainer that is wired to the battery isolator from both banks of batteries.
If I unhook the wire from the chassis battery side of the isolator that comes from the battery maintainer the buzzing stops and there is no power going to the ignition until i turn on the disconnect switch.

Is my battery Isolator bad or is my battery maintainer bad?

It has me baffled.

Maintainer is leaking current. Replace it or add a diode to the chassis side wire.