Two weeks ago, while in the Escapees park in Alabama, turned on the Aquahot diesel. Green led came on, motor started and ran, all good. A few minutes later Molly let me know she wasn't getting hot water. In our house, that's an emergency.
Checked outside, motor running but exhaust was cool. Checked the 120v and 12v breakers. Both good. Pulled the cover from the Aquahot, replaced six 12v fuses. No help. Pulled the Aquahot thermostat cover, found my troubleshooting guide doesn't match this Aquahot. We have four thermostats, not three, and we don't have an overtemp reset switch.
Time for the big guns, called Rudy Legett. Had me pull out the volt meter and very patiently helped me figure out how to use it. Led me through the various connections on the terminal board and the brain box. Provisional diagnosis was bad brain box. Molly pointed out she could have told me this a lot sooner. Rudy called Roger Berke to confirm, then had me do a couple more checks to confirm.
Crossed my fingers, ordered a new brain box from Roger. He had it in the mail an hour later. Two days later, and $800 poorer, the brain box was installed and we had hot water.
This is my long winded way of saying thanks to Rudy and Roger. If you have problems with your Aquahot and you're anywhere near Baytown, go see Rudy. If you're not near Baytown, call Aquahot, visit Roger's forum, or send Rudy a pm.
Rudy is the goto person, that is for sure. He is a great resource for all of us.
+1 - Rudy.
Did they ask for your brain box as a core? I'd be interested in examining these things to find out what fails.