Rheem Tankless Error Code Troubleshooting

What it Means: Continual combustion for more than 1 hour – This unit isn’t designed to run continuously with the circulation system.

How to Fix: Turn off all hot water taps to reset the unit. You may also need to turn off or replace the circulation system.

What it Means: Imperfect Combustion – The system is dirty or blocked.

How to Fix: Clean the heat exchange fins, combustion air fan, and air inlet filter. Check the ventilation system and vent openings for blockages or dirt and clean as needed.

What it Means: A false flame has been detected.

How to Fix: Check to ensure all vent and heat exchange components are clean and properly connected. Make sure the flue inlet and exhaust are free of blockage. Additionally, make sure the proper vent materials were used.

What it Means: There’s no ignition.

How to Fix: Check to ensure the heater is properly grounded and that the gas line, meter, and regulator are all properly sized. Check the gas solenoid for valves for short circuits and the igniter wiring harness for signs of damage. Bleed any air from the gas lines. Ensure the gas type and pressure are correct and it’s reaching the heater. Finally, check the igniter to ensure it’s functional.

What it Means: Flame failure: The heater can’t maintain a flame.

How to Fix: Check for proper grounding and that the device is receiving gas of the right type and pressure.Examine the flame rod to ensure it’s connected and has no carbon buildup. Disconnect the remote control, PC board, and all wiring harnesses, then reconnect.

Ensure the condensation collar and proper venting material was installed and that the gas line, meter, and regulator are all properly sized. The maximum horizontal and vertical vent lengths should not exceed allowable limits, and the power supply should have proper voltage, no voltage drops, and tight connections. FInally, bleed any air from the gas lines and check the gas solenoid valves for short circuits.

What it Means: There’s a fault in the Overheat Wrap.

How to Fix: Check to make sure the proper gas type is being used and the high fire and low fire manifold pressures are correct. Examine the heat exchanger for cracks or other openings, as well as air flow restrictions around the vent terminal and unit. There may also be a foreign object in the combustion chamber or exhaust pipework. Finally, Ohm out the safety circuit.

What it Means: This is a boiling safety warning.

How to Fix: The cold water inlet pipe and inlet valve should be fully open. Also, check to ensure there’s no scale blocking the heat exchanger.

What it Means: Over Temperature Warning – The heater has exceeded safe heat levels.

How to Fix: Check the combustion chamber, exhaust pipes, heat exchanger, and vent terminal for scale or blockages.

What it Means: There’s a malfunction in the air intake filter switch.

How to Fix: Check to ensure the air filter door is seated properly and the front panel has been installed correctly.

What it Means: There’s a malfunction in the operational switch.

How to Fix: Press the max button, then the min button to reset the switch. In the event this doesn’t work, you’ll need to replace the PCB.

What it Means: The heat exchanger output temperature is too low.

How to Fix: Clean the heat exchanger air inlet.

What it Means: There’s a fault in the water inlet temperature sensor.

How to Fix: Check the sensor wiring for any damage and clean off any scale. Ohm out the sensor, replacing it if necessary.

What it Means: There’s a fault in the outgoing water temperature sensor.

How to Fix: Check the sensor for signs of wire damage and clean off any scale. Ohm out the sensor and replace if necessary.

What it Means: There’s a fault in the combustion air temperature sensor.

How to Fix: Clean any scale from the sensor and check it for damage. Make sure there are no restrictions to the air flow. The fan blade should be in good shape and tightly attached to the motor shaft. Ohm out the sensor and replace, if necessary.

What it Means: The thermistor is incorrectly connected.

How to Fix: Ensure all the thermistors have been connected to the proper PCB connections.

What it Means: There’s a fault in the gas inlet solenoid valve.

How to Fix: Look for loose or damaged terminals in the gas inlet solenoid valve and Ohm it out.

What it Means: There’s a fault in the modulating solenoid valve.

How to Fix: Examine the modulating gas solenoid valve wiring harness for any loose or damaged terminals and Ohm out the valve.

What it Means: Combustion Fan Failure – The combustion fan isn’t turning properly.

How to Fix: Check to make sure there’s no damage to the wiring harness or motor and all connections are tight. The fan motor should turn with minimal resistance. You may also wish to Ohm out the motor winding.

What it Means: There’s a fault in the gas inlet solenoid valve control.

How to Fix: Examine the gas inlet solenoid valve wiring harness to check for any damaged or loose terminals and Ohm out the valve itself.

What it Means: There’s a fault in the flame sensing device.

How to Fix: There is likely an issue with the flame rod. Ensure the wiring is undamaged and providing the proper voltage. Remove the flame rod and clean off any carbon buildup with sandpaper. Replace the rod, making sure it touches the flame when firing and there are no foreign materials getting in the way.

What it Means: Communication error with remote control.

How to Fix: Make sure there’s no damaged or loose connections. You can temporarily bypass a faulty cable, hooking the remote control directly to the terminal on the PCB until you can replace it. In an extreme case, you may have to replace the remote control or PCB.

What it Means: There’s a fault in the fan motor current.

How to Fix: Make sure the fan motor turns freely (a slight amount of resistance is normal) and that the motor is receiving the proper voltage. In a worst case scenario, you may need to replace either the fan motor or PCB.

What it Means: The gas cut-off has failed.

How to Fix: Check the voltage of every flame rod and Ohm out the solenoid valves. Replace the gas control valve, if necessary.

What it Means: There’s a problem with determining the gas type.

How to Fix: Program the PCB for the proper gas type.

What it Means: The flue is blocked.

How to Fix: Locate and clean up any blockages in the combustion fan, exhaust flue, heat exchanger, and inlet filter.

What it Means: Nothing’s happening when water flows through the device.

How to Fix: There are several possible causes for this issue. Ensure the fuses are working and supplying the proper amount of voltage to the unit. Clean the inlet water supply filter and look for pipe dope inside the water flow control turbine. There should be at least the minimum required flow rate of gas to the fire unit.

Another potential cause happens mostly with freshly installed units. Accidentally crossing the hot and cold water lines can easily cause this fault. Similarly, bleed over in current installations can create an error. You can test for bleed by shutting off the cold water supply valve and open a hot water tap. Steady flow is a clear sign of bleed over. You’ll need to contact a professional to fix the bleed issue.