10 Common Rheem Furnace Error Codes And What They Mean

When you’re maintaining the mechanical parts of your home, such as a heating system or water heater, it can be challenging to identify the exact problem that’s occurring. Some numerous codes and indicators pop up from time to time, but what do they mean? What is causing this code to appear on your device? These codes may appear randomly from time to time, which can make troubleshooting that much more difficult. Fortunately, if you’ve experienced one of these common Rheem furnace error codes and what they mean before, it will become much easier for you to address the problem and get your system back up and running again. Stay informed about the status of your heating system so that you can catch any problems early on before they escalate. Here are 10 common Rheem furnace error codes and what they mean:

Rheem Furnace Error Code 10

When a furnace error code 10 pops up, it’s usually due to a problem with the sensor that’s registering air flow and temperature. This could be any number of sensors, including the hot sensor, cold sensor, or even the flow sensor. If any of those sensors are experiencing a problem and sending the wrong information, it could result in an error code 10. If you receive error code 10, inspect the sensors and make sure that they are not blocked. If there is a significant clog, a slight repositioning of the sensor may be enough to clear out the issue. If you still see an error code after you’ve cleared the sensors, you will likely need to replace the sensor.

Rheem Furnace Error Code 12

Depending on what it is, error code 12 could be a serious problem or a simple fix. It could mean that the temperature inside the furnace is too high, which could pose a risk of fire. However, it could also just mean that there is too much water in the furnace since a 12 is also the code for a water leak. The first thing to check if you get this error code is the temperature gauge. If it’s above normal, you may need to open up the furnace and check for a buildup of lint or debris. If there is water inside the furnace, it could mean that the water pump is leaking or that there is a crack in the water line.

Rheem Furnace Error Code 21

A problem with the blower motor could result in an error code 21. If you have to replace the blower motor, be sure to check the fan blades while you’re in there. If they are bent or broken, they may be impeding the motor’s ability to run properly. If the error code persists, you may need to replace the furnace entirely. The blower motor may be faulty and cannot be repaired. A broken blower motor can lead to overheating, so it’s best to have it replaced as soon as possible to avoid any further damage.

Rheem Furnace Error Code 23

A furnace error code 23 could be an indication of a problem with the thermostat. If the thermostat is set to the wrong temperature, it could be the source of this error code. The thermostat might be broken or set at an incorrect temperature. You may also be dealing with a wiring issue if you receive this error code. The wiring between the thermostat and furnace could be broken, causing the two devices not to communicate properly. If you receive error code 23, you should check the thermostat settings and make sure that they match the environment. If the settings appear normal, you may need to replace the thermostat.


If you’ve received a furnace error code, don’t panic! These codes are simply indicators of potential problems in your heating system. By staying informed about the status of your system and what these codes mean, you can easily resolve the issues and get your system back up and running again.