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


This model is a MAJOR redesign of HHE-x00-07x


Exactly like HHE-x00-07x except


  • Zone pumps now have plastic covers over the moving parts
  • Engine preheat pump is PLE-100-830 - Stir Pump. NOT AVAILABLE
  • On this model the entire drain valve is plastic. Replace with Drain Valve Kit or Brass Drain Valve Kit
  • Use ELX-630-001 electric relay or ELE-630-002-FRU kit that already has the relay attached to a cover.
  • Has regular size radiator cap.
  • Filled with Camco -100 Boiler coolant.  First model in the Hydro-Hot series to use the special coolant.


Serial number 3653 to .....

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 ‘clip on’ Low Temperature Cutoff Thermostat - ELE-LTC-505
  • Electric system uses electronic relay, which did not hold up well.   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-x00-08x - Brass

Service Manual


On Aqua-Hot website   HHE-200-08E  Scroll down page in "Discontinued Hydro-Hot Products" section