So, we got the battery tested and it's right as rain.
We also reattached the ground wires securely to a newly cleaned and tightened bolt in the frame. I also opened up the converter box and tightened the screws in the ground bar at the converter.
However, the problem persists. Ruling out the battery and the most obvious places for a loose ground connection really only leaves us with a few options.
This leads me to think it's either the converter or we have a problem with some loose wiring in the connection to the water heater.
A replacement for the converter is about $300, so I would hate to do that work and then find out that it wasn't the problem.
On the other hand, the converter is operating out a spec with an output of 17amps when the fuses are plugged in. That makes me think it needs to be replaced regardless, as it's overcharging our battery.
I will go through and check my wiring job in the most accessible places in the back of the cabinet, but I think this means a converter replacement.
Unless there is some merit to the idea that plugging into a 15amp plug is causing DC electrical issues? But from what I've read, people do this all the time without issues and the only issue it should cause is possibly tripping the breaker if we tried to pull too many amps.
