The Aqua Hot or Hydro Hot are unique and common only in diesel pushers. The guts come from Germany with a computer. It was originally designed for boats with a brand name of Webasto. It is then adapted by Aqua-Hot, with a second computer, to work in motorhomes. There are three or more pumps, some check valves, a mixing valve and multiple sensors, let alone the thermostats that can run both it and the air conditioners of yet a different brand.
You can replace a typical RV propane furnace for about $500. If you need to replace your Hydro/Aqua Hot, it will cost about $8,000. The German computer is sealed in a little metal box, has three mechanical relays in it along with electronics. If one of those relays starts to stick, the part is $900. It is that complex!
The basic check routine check is to see if the exhaust is clear after the first few puffs, the overflow tank has coolant between the marks, the coolant level in the overflow tank goes down when you shut it off and up when it is hot, that you get reasonably hot water and heat from all the vents.
If you need to add a little coolant, use the right stuff. Yours is old enough it probably has plain automotive antifreeze. Newer ones need expensive "boiler coolant". The coolant subject has lots of experts, but until you compare you serial number to the list of "old" vs "new" you can get it wrong.
Basic annual service is the replacement of the burner nozzle, fuel filter, internal cleaning and adjustment of the ignitors. And it is not that difficult. But, if the tech has not been to Hydro/Aqua Hot school, I would not let them touch it.
In nine years I've had half a dozen repairs. Three are memorable because they were expensive, the techs had not gone to school and there work needed post repair attention. In one case, the business was on the list, but the tech had quit and taken his tools with him! (That's the repair that ended in a new $900 Webasto computer, with mechanical relays.)
The website listing techs that have gone to school and are "approved" is
http://www.aquahot.com/Service-Help/Service-Locations.aspx . On that list is BAC member (and Beaver owner) Orman Claxton. The website provides his number as 206-660-9893. He has been known to insist that members call him for advice. You'll see him at some of the bigger Beaver rallies.
I like Camping World and shop there. Unless the specific store is on the list, I would never take a Hydro Hot to them.
To drive my point home, I met a camper with a new to him motorhome when I was a camp host in a state park. He asked if I could help get hot water for his wife's shower. I tried to help until I noticed water running from the bottom of his motorhome. I asked him how he winterized it and got, "same as every other RV I've ever owned." He wouldn't talk to me the rest of the weekend after I told him the repair was going to cost around $8k!
