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Rinnai · Tankless water heater troubleshooting

Weak or missing flame signal (flame rod checks)

What is going on

Electrical checks for a flame rod circuit that reads low, from the Electrical Diagnostics page.

Likely causes

  • Carbon or damage on the flame rod
  • Loose or damaged flame rod wiring
  • Old flame rod gasket reused

Check in this order

  1. With the heater running, measure AC volts between the flame rod and ground; a healthy rod reads roughly 5 to 150 VAC.
  2. Put the meter on the microamp range in series with the rod; 1 microamp or more is a good flame circuit.
  3. If the signal is low, remove the rod, inspect it for carbon or damage and clean or replace it.
  4. Always fit a new flame rod gasket after the rod has been removed.

Applies to: SENSEI RX/CX (RX199i, RX180i, RX160i, RX130i, CX199i, CX160i, RXP199i, RXP160i, CXP199i, CXP160i)

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Source: Rinnai SENSEI RX/CX technical guide U362-0875, Electrical Diagnostics. Written in our own words; check the manual for your exact model.

For licensed technicians. Gas, electrical and refrigerant work must be done by a qualified, licensed person. Shut off power and gas before servicing, never bypass a safety control, and follow the manufacturer’s manual for the exact model; it and local codes always take priority. HVACopedia is not affiliated with any manufacturer; brand and model names only identify the equipment.