Rheem Tankless Water Heater Error Codes: Complete Diagnostic List
29 diagnostic codes documented · Official site ↗
🟡 Warning — Schedule Service
Rheem Code 10 - Air Supply or Exhaust Blockage
Indicates blocked air intake or exhaust venting. The unit detects insufficient combustion air supply or restricted exhaust gas flow.
Rheem Code 29 - Fan Motor Abnormality
Rheem error code 29 indicates an abnormality with the fan motor. This usually means the system's control board isn't receiving the expected feedback from the fan, or that the fan isn't operating within the expected speed range. The fan motor is responsible for exhausting combustion gases safely out of your home. When it malfunctions, the system shuts down as a safety precaution to prevent dangerous gases from building up inside your home. This code can appear on tankless water heaters or furnaces.
Ignition Failure
The A001 error code on your Rheem HVAC system indicates that the ignition system isn't functioning correctly. This could be due to a faulty ignition control module, a problem with the igniter, or an issue with the gas valve. The system is designed to protect itself from potential hazards, so it's displaying this error and may not be operating at full capacity.
Abnormal Ignition
The A003 error on your Rheem HVAC system indicates an abnormal ignition issue. This could mean that the system is having trouble igniting the burner or keeping it lit. This is likely due to a problem with the ignition system or the gas supply. Don't worry, it's safe to troubleshoot, but it's recommended to call a professional for repair.
False Flame Detection
The A004 error on your Rheem furnace indicates a false flame detection issue. This means the system's flame sensor has detected a flame when there shouldn't be one, causing the furnace to shut down to prevent potential damage. This is a safety feature, but it's important to address the underlying cause to restore proper function.
Exhaust Temperature High
The A008 error code on your Rheem HVAC system indicates that the exhaust temperature has exceeded the safe limit. This could be due to a variety of reasons, including a faulty temperature sensor, a clogged exhaust vent, or a problem with the heat exchanger. It's important to address this issue promptly to prevent further damage to your system.
No Flame Detected
The 'No Flame Detected' (A011) error on your Rheem furnace indicates that the system has failed to ignite or maintain a flame. This could be due to a variety of reasons, but it's crucial to address this issue promptly to prevent further damage and ensure your furnace is operating safely.
Over-Temperature
The A021 error code on your Rheem HVAC system indicates that the unit has reached an unsafe temperature. This is likely due to a malfunction in the system's temperature control or a problem with the cooling components. The system has automatically shut down to prevent damage or safety hazards. It's important to address this issue promptly to avoid further damage or potential safety risks.
Inlet Thermistor Open/Short
The Rheem A031 error code indicates that there's an open or short circuit in the inlet thermistor, which is responsible for measuring the temperature of the incoming air. This could be due to a faulty thermistor, a broken wire, or a problem with the circuit board. The system has entered a safety lockout mode to protect itself from further damage. You'll need to address this issue to restore normal operation.
Outlet Thermistor Open/Short
The A041 error code on your Rheem HVAC system indicates a problem with the outlet thermistor. This component is responsible for measuring the temperature of the air leaving your system. If it's open or shorted, your system can't accurately monitor and control the air temperature, leading to comfort issues and potential system damage. This error will cause your system to enter lockout mode, displaying the A041 code on your display.
Water Level Error
The A043 error code on your Rheem HVAC system indicates that the water level in the system is either too high or too low. This could be due to a faulty water level sensor, a leak in the system, or a problem with the water supply or drainage. It's important to address this issue promptly to prevent further damage to your system.
Fan Motor Abnormality
The Rheem A051 error code indicates that your HVAC system has identified an unusual operation in the fan motor. This could be due to a variety of reasons, but it's important to have it checked by a professional to prevent potential damage to your system. The fan motor is a crucial component that ensures proper airflow and heat exchange in your HVAC system.
Fan Motor Speed Error
The A052 error on your Rheem HVAC system indicates a problem with the fan motor speed. This could be due to an issue with the control board, the fan motor itself, or the wiring connecting them. The system may run at the wrong speed, or the fan may not run at all. This can lead to reduced comfort and higher energy bills.
Fan Motor Open Circuit
The A053 error on your Rheem HVAC system indicates that there's an open circuit in the fan motor's electrical system. This could be due to a broken wire, a faulty motor, or a problem with the motor's control board. The system is still running, but the fan motor isn't getting the power it needs to operate. It's important to address this issue promptly to prevent further damage to your HVAC system.
Fan Motor Overcurrent
The Rheem A054 error code indicates that the fan motor in your HVAC system is drawing more current than it should. This could be due to an obstruction in the fan, a faulty motor, or an issue with the control board. It's important to address this issue promptly to prevent further damage to your system.
Fan Motor Locked
The Rheem A055 error code indicates that your system's fan motor has locked up, preventing it from running. This could be due to an obstruction, a faulty motor, or an issue with the motor's control circuit. The system has automatically shut down to prevent damage or fire hazard. Do not attempt to restart the system until the issue is resolved.
Fan Speed Error
The Rheem A061 error code indicates that your HVAC system's fan isn't operating at the correct speed. This could be due to a faulty fan control board, a problem with the fan motor itself, or an issue with the system's wiring. The fan may run too fast, too slow, or not at all. While the system is still functional, it's important to address this issue to maintain optimal performance and prevent further damage.
Gas Valve Circuit Error
The A071 error on your Rheem HVAC system indicates a problem with the gas valve circuit. This circuit controls the gas flow to your furnace's burner. The system has temporarily shut down the gas supply to ensure safety. You can continue using your system in fan-only mode, but it won't provide heat until the issue is resolved.
Water Flow Control Error
The A081 error code on your Rheem HVAC system indicates a water flow control issue. This could be due to a blockage in the water flow, a faulty water flow switch, or an issue with the system's water pump. It's important to address this issue promptly to prevent further damage to your system.
PCB Communication Error
The Rheem A091 error code indicates a communication issue between the main PCB (Printed Circuit Board) and other system components. This could be due to a faulty wire, connector, or the PCB itself. The system may not operate correctly or might display other error codes as a result.
PCB Data Error
The A093 error code on your Rheem HVAC system indicates a problem with the data being read from the printed circuit board (PCB). This could be due to a faulty sensor, a broken wire, or a problem with the PCB itself. The system has locked out to prevent any further issues, and you'll need to reset it after the problem has been fixed.
DIP Switch Error
The Rheem A095 error code indicates a problem with the DIP switches on your HVAC control board. DIP switches are small, removable components that allow you to set specific parameters for your system. When the system detects an issue with these switches, it displays the A095 code and may lock out certain functions.
PCB Failure
The A099 error on Rheem systems indicates a failure of the main control board (PCB). This board controls all system functions, including ignition, fan speed, temperature sensing, and communication with thermostats. When it fails, the system cannot operate correctly or at all. This is typically a hardware failure—often a relay stuck open or closed, a failed capacitor on the board, or a burned trace from a power surge. It can also be triggered by a low-voltage short from the thermostat or zone panel. The board itself is not user-serviceable; it must be replaced by a qualified technician. On Rheem gas furnaces (like the R801T) and air handlers (like the RH2T), this error usually locks the system out, meaning it won't attempt to start again until power is cycled or the thermostat calls again. On Rheem heat pumps (like the RP16), it may also disable the outdoor unit.
Condensate Blockage
The Rheem A101 error code indicates that your HVAC system has detected a blockage in the condensate drain line. This line is responsible for removing the moisture created during the cooling process. If left unchecked, this blockage can cause water to back up and potentially overflow, leading to water damage in your home. It's important to address this issue as soon as possible to prevent any potential damage.
Bypass Valve Error
The A121 error on your Rheem HVAC system indicates a problem with the bypass valve, which is part of the reversing valve assembly. This valve switches the refrigerant flow between heating and cooling modes. When it malfunctions, your system may not switch modes correctly, leading to comfort issues. The error code A121 usually means the valve is stuck in one position or not responding to commands.
Rheem Code P1 - Defrost Error
The P1 error code on your Rheem heat pump indicates a problem during the defrost cycle. Heat pumps move heat from outside to inside your home. When it's cold outside, frost can build up on the outdoor coil, reducing its ability to absorb heat. To combat this, the heat pump periodically goes into 'defrost' mode to melt the ice. The P1 error means the system isn't defrosting correctly, potentially due to a faulty sensor, a problem with the reversing valve, or airflow issues. Ignoring this can lead to the heat pump completely freezing up, causing further damage and leaving you without heat.
🔴 Critical — Shut Down Immediately
Rheem Code 11 - No Ignition
Rheem error code 11 signals that your tankless water heater attempted to ignite the burner but failed. This means the unit went through its startup sequence, including the fan starting and the igniter sparking, but the main burner flame didn't establish itself. The water heater will typically try a few times before locking out on this error. This is a critical safety issue because unburned gas can accumulate, creating a risk of explosion or carbon monoxide poisoning. It's important to address this problem right away to ensure your safety and the proper operation of your water heater.
Rheem Code 12 - Flame Failure
Rheem tankless water heaters are designed with multiple safety features. A Code 12, or Flame Failure error, means the unit tried to ignite the burner, but the flame wasn't properly detected or was lost during operation. This is a critical safety issue because unburnt gas can accumulate inside the unit and potentially create a hazardous situation. The system locks out as a safety measure. This error can occur during initial startup, during normal operation, or after a period of inactivity. It's important to address this issue promptly to ensure safe and reliable hot water.
Rheem Code 13 - Incomplete Combustion
Rheem tankless water heaters and furnaces are designed with safety in mind. When the system detects incomplete combustion, meaning the fuel isn't burning completely, it shuts down and displays error code 13. This is a critical safety feature because incomplete combustion can release carbon monoxide (CO), a colorless, odorless, and potentially deadly gas. This error can stem from various issues affecting the air-fuel mixture or the venting system. It's important to address this issue promptly to ensure your safety and the proper operation of your Rheem unit. Because CO is so dangerous, troubleshooting should be left to qualified technicians.