IOTA Automatic Transfer Switch changed. Now there is an electrical problem (short?).

[n4248z]

I replaced the IOTA with the LYGHT LPT50BRD ATS. I turned off shore power (30amp) and turned off house battery cutoff switch before making the change and then turned both back on. Everything seemed fine. I turned off the shore power and ran the generator. I ran the ac units one at a time. I shut down the generator and turned the shore power back on.

Some background: 2004 Monaco LaPalma. In 2019 I replaced the 2003 XANTREX 81- 2021 inverter with XANTREX 81-2022. In 2020 I replaced the 4 - 6 volt deep cell house batteries.

The inverter is in the rear bay and the batteries are in the next bay with only the compartment wall of the bays separating them. I could hear a loud "electrical hum" that seemed to be from the 300 watt Integrated Power System fuse that is mounted on the common bay wall. A 9 amp draw was displayed on the Progressive EMS LCHW50 that is installed between the 50 amp shore power cord and the ATS. Nothing in the coach was on. Normally there is no amp draw except when putting the rear slide in or out as the coach is "stored" at my residence for the summer. I disconnected the shore power. The battery's status indicator dropped from good to fair. I left things that way overnight. The next day the battery's indicator read even weaker. The cable from the inverter to the fuse and going from the fuse was hot. I turned off the house battery cutoff switch (in the bay with the batteries and fuse) and the humming stopped and the cables cooled down to normal after a period of time.

I load tested each of the batteries with the cables unhooked. They all tested fine. I have a new fuse, but before I change it I need to find the reason for these issues. I know this is difficult to diagnose from a distance. Any ideas and suggestions are welcomed and appreciated.