Rheem 305, 505, 705 Error 33: Heat Exchanger Outgoing Temperature Sensor Fault

Tankless water heater · taken from the manufacturer’s manual, pages cited

Fault code33

Heat Exchanger Outgoing Temperature Sensor Fault indicates sensor wiring damage or scale build-up on the sensor. The manual's first action is: “Measure resistance of sensor.”

Model
Rheem 305, 505, 705
Display shows
Heat Exchanger Outgoing Temperature Sensor Fault (33)
Type
Fault code
Source
Manual p. 10

What 33 means

Heat Exchanger Outgoing Temperature Sensor Fault p. 10

Common causes

  • Check sensor wiring for damage. p. 10
  • Clean sensor of scale build-up. p. 10

What to do

  1. Measure resistance of sensor. p. 10
  2. Replace sensor. p. 10

Before you service the product, read the safety instructions in the manual p. 4.

If 33 is still not resolved

  • Immediately call your gas supplier from a neighbor’s phone. p. 1
    “Immediately call your gas supp lier from a neighbor’s phone.”
  • If you cannot reach your gas supplier, call the fire department. p. 1
    “If you cannot reach your gas supplier, call the fire department.”
Open the manual at page 10 All 305, 505, 705 error codes Manual details & download

This page summarises what the manufacturer’s manual says about 33; each statement links to the page it comes from, and quoted lines are copied word for word. It is not a substitute for the manual or for a qualified installer. ManualLib is not affiliated with Rheem. Found a mistake? Report an error.