RV Hydronic Heater Repair



The models ending in "E" were built with engine preheat pump

The models ending in "M" were built with NO engine preheat pump

   Many units have been retrofitted with engine preheat pump



This model of Aqua-Hot uses the special Camco -100 Boiler coolant.




This model may also be known as:



Note that the 200 and 500 series use the same components

Changes From Previous Model


  • Low Temp Cutoff Thermostat now screws into port on incoming cold water supply, which seems to work better.  ELE-000-606
  • On this model the drain valve has brass nipple screwed into boiler tank, with rest of drain PEX. Replace with Drain Valve Kit or Brass Drain Valve Kit (see Part# below)

Part Notes


  • Control Thermostat -   ELE-014-010
  • Electric high limit thermostat - ELE-HLT-322   -or- with terminals crimped on  ELE-ASY-200-HYD
  • Diesel high limit thermostat -  ELE-HLT-322 
  • Control Board -  ELE-PC4-010  This control board will directly replace the 008 and 009 models.  You may have to crimp different (larger) terminals on 12-VDC supply wires.
  • Tank level sensor (float switch) - ELX-800-002 - Brass float
  • Zone, stir and engine preheat pumps (are no longer available).  Pump upgrade kit, here: PLE-100-905-FRU
  • Radiator cap - PLX-102-229
  • Uses 'screw in’ Low Temperature Cutoff Thermostat - ELE-000-606
  • Electric system replacement electric relay pop riveted to cover  ELE-630-002-FRU
  • Reconditioned Webasto burner - WPE-905-834-R



Routine service parts and kits - Routine Service Parts      Scroll down page for filter and nozzle packages.



Common Problems


  • Stir pump failure -  Upgrade kit, here:  PLE-100-905-FRU
  • PLASTIC DRAIN valve.  If you still have plastic in the drain valve, you should immediately replace it with brass,

                                                                                              here:  Drain Valve Kit - HHE-x00-09x - Brass

Service Manual


On Aqua-Hot website   HHE-200-09E  Scroll down page in "Discontinued Hydro-Hot Products" section