RV Hydronic Heater Repair

431 prior to serial number 94180

This model may also be known as:


920/431, 920431/12, 920/432, 431


Most of these heaters were 12-volt,

however there were a few 24-volt heaters built.

This model of Aqua-Hot uses 'standard' ethylene glycol coolant (Prestone or equal).  Keep it simple and use the same coolant that is in your engine and generator.



Part Notes


Thermostats are ELX-560-213, which are no longer available. 


3 zones + engine circulation pump PLX-809-200    Used pump, here:  PLX-809-200-U


1650 watt electric element ELX-2E7-540  Note: that electric element rarely fails! 
Most failures in electric system is electric high limit thermostat.


Mixing valve (complete) PLX-4A8-180 - Rebuild kit PLX-4A8-18R


Radiator Cap - PLX-102-229 or with lever PLX-102-229-L

Routine Maintenance


Replace filter and nozzle when exhaust gets smoky / smelly.  Aqua-Hot recommends yearly routine service.


Radiator cap should be replaced at least every other year (or as often as needed).  PLE-102-229  or Cap with Lever PLE-108-229-L

Recommended Service Parts to Keep On Hand


Filter:  VERIFY FILTER:  Normally one of filters below. 

Webasto - WPX-603-359


Racor R12T  FLE-R12-TRA


Nozzle:  WPX-886-41A


Optional Service Parts to Keep On Hand



Service Manual


AHE-100-02S - On Aqua-Hot website