I'm not sure about the InCommand system. I do not have it.
There is a 5A fuse on the back of the control panel where the electric water heater switch is.
Since it works on propane it's probably good.
The 120vac relay (activated by 12vdc) is on the top left side of the water heater. You have to remove the water heater to get to it.
I wrote about mine coming loose and reinstalling it (with pictures)
https://www.montanaowners.com/forums...ad.php?t=86637
Pretty easy task.
Someone else had to replace that relay. Picture below.
Also there is a Suburban water heater manual in the files section with the wiring diagram. The 120vac side is very simple to trace.