Rheem 305, 505, 705 Error 72: Flame Sensing Device Fault

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

Fault code72

Flame Sensing Device Fault occurs when the flame rod isn't touching the flame, has carbon build-up, or micro amp output is abnormal. The manual's first action is: “Check all wiring to flame rod for damage.”

Model
Rheem 305, 505, 705
Display shows
Flame Sensing Device Fault (72)
Type
Fault code
Source
Manual p. 10

What 72 means

Flame Sensing Device Fault p. 10

Common causes

  • Ensure flame rod is touching flame when unit fires. p. 10
  • Remove flame rod and check for carbon build-up; clean with sand paper. p. 10
  • Measure micro amp output of sensor circuit with flame present. p. 10

What to do

  1. Check all wiring to flame rod for damage. p. 10
  2. Check inside burner chamber for any foreign material blocking flame at flame rod. p. 10
  3. Replace flame rod. p. 10

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

If 72 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 72; 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.