I have a 2005 38 FDTS LTD so your systems should be close if not the same as mine, depends upon options and if you have an APEX. First a couple of questions. 1) do you have the heat pump option? 2) have there been any modifications to the heating system? 3) what type of thermostat do you have?
I have a replacement t stat (the old one died) that has a separate setting for the HP, so I have a setting for HP and one for hydro hot.
The Hydro Hot heats on 3 sources the switch should be in you utility closet near the t stat.
1) diesel - turn on the "diesel" switch, set the t stat.
2) electric - turn on the "electric" switch, set the t stat, there is not much volume of hot water in this mode but if you are careful you can do dishes and take a quick shower. If I am on shore power I leave this switch on all the time.
3) engine - no switches on, while you are driving the engine heats the hydro hot and you get "free" heat, just set the t stat.
You can also use the Hydro Hot to pre heat the engine, just turn on the preheat switch.
You will have 2 zones, the front of the coach and the rear. You should also have a hidden zone, the basement, there is an adjustment for the temperature on the ceiling of the basement, mine is near the Glendinning power reel, I have never changed it, the basement stays warm where it was set by WRV.
Let me know if you have any other questions.
Dave, Bobbi and Fenway
2005 38' FDTS Alpine Limited, 2016 Jeep Grand Cherokee Limited
Cape Cod, MA