I can only reply to the Aquahot as this is what we have in our 2004 Beaver Marquis.
IF you go to the www.aquahot.com website you can download the manual and the parts manual for your units aquahot.
The model number is on the front of your unit about halfway back from the compartment opening, you will need a mirror to be able to read.
Our model was 103 pages long but well worth the time and reading it made a lot more sense as to how and why it works. Parts manual also has several parts I will have as spares now that I understand why. Numerous pictures if you do not like to read.
They look complicated but are actually quite simple once you understand what and how they do it. Wonder why a Coach cost what it does, New Aquahot $10,000.00 refurbished $7,000.00. Trust me you can repair your own with a little help from this forum and a decent mechanic, and the manual.
I am currently completing a bypass for the Aquahot so I can heat the Coach while in its bay for winter with our wood fired boiler. It has taken a little ingenuity to understand that you must totally bypass the aquahot and drain the domestic water line around the boiler heat chamber as the diesel burner or electric will not heat the copper lines wrapped around the heat chamber. No residual heat will be there either.
( I have talked to Aquahot service numerous times and with the systems regulated thru a circuit board it is impossible to seperate them to operate the zone pumps without having the diesel burner or electric firing the boiler). The Coach will have its own zone pump off the wood boiler and the coach thermostats will operate as they normally do to regulate the zone heat desired right thru the plate heat exchangers and blowers under the cabinets and bed.