How to Read Rheem Furnace Error Codes and How to Fix it

Posted by: Mas Broto
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Rheem Furnace Error Codes

This Rheem error codes guide is made for the person who might want to try and fix their furnace. I wanted to list the Rheem furnace error codes with some guidance on what the possible underlying issues could be to make these errors appear. Understanding these codes can make troubleshooting a breeze.

Rheem furnaces are designed with an advanced 7-segment diagnostic display. They don’t use flashing LED light sequences to indicate errors, like other brands. Rheem and York give you a simple error code that you can use for diagnostics of your furnace problems.

Rheem advanced 7-segment diagnostic display

Rheem Furnace Error Codes

There have been many times I have seen furnace error present itself, but the cause of this error is not necessarily what it shows. I will try and give you the best possible diagnosis and a description of what you can do to fix the error.

Here, we will list the meaning of specific Rheem error codes and how to read it.

Rheem Furnace Normal Operation Codes

Just as Rheem furnaces have error codes that indicate potential issues, they also utilize codes to signify normal or standard operating procedures. Understanding these can provide peace of mind when monitoring your furnace’s function.

cY1 on (Legacy Mode Only)
CY2 or Any Communicating Cooling Call
dFDefrost active
FContinuous fan
H flashingFurnace Calibration
HFurnace Heat
hGas heat – No “V” Signal (Legacy Mode Only
h flashingCalibration – No “V Signal (Legacy Mode Only
cd or CdDehumidification active (Legacy Mode Only)

Rheem Furnace Shared Data Error

Shared data errors in your Rheem furnace relate to communication problems between the main control board and other essential components of the system. When components can’t “talk” to each other properly, you might run into efficiency issues or even a complete shutdown. Let’s dive into what these errors mean and how to address them:

d1No Shared Data
d3Airflow Mismatch
d4Memor Card Invalid
d5Card-Hardware Conflict
d6Blower Horsepower Conflic
d7Blower Manufacturer Conflict
d8Old Shared Data

Wiring Inspection: The first step is to ensure that all the wires connecting the main control board to the user interface (like the thermostat or other control panels) are securely connected. Look for any loose, corroded, or damaged wires and connections.

Reset the System: Sometimes, a simple power cycle can restore proper communication. Turn off the furnace, wait a few minutes, and then turn it back on. This might reset the system and clear any minor glitches.

Control Board Assessment: The control board itself might be at fault. If you’ve ruled out other issues and still face the communication error, consider consulting an HVAC professional to assess the control board’s functionality.

Addressing shared data errors often requires a methodical approach, eliminating one potential cause at a time. If you’ve run through the suggested troubleshooting steps and the issue persists, it might be time to consult with a Rheem professional. They’ll have specialized tools and expertise to diagnose and fix the problem efficiently.

Rheem Furnace Flame Sense Signal Error Codes

10One Hour Lockout
11Failed Ignition
12Low Flame Sense
13Flame Lost
14Unexpected Flame

Gas Supply Check: Sometimes, the simplest explanation is the right one. Ensure that your gas valve is in the ‘ON’ position. If the gas supply was off, turning it on should resolve the problem.

Ignition System Inspection: If your gas is flowing but you’re still receiving this error, there’s a chance your ignition system isn’t working properly. This could be due to a faulty igniter, flame sensor, or a disrupted connection. Cleaning the flame sensor with a soft cloth can sometimes do the trick. If the problem persists, you may need to replace the sensor or get a professional to inspect the ignition system further.

Rheem Furnace Limit Control Error Codes

22Main Limit Open
23Heat Assist Limit (HALC) Open
33Manual Reset Limt (MRLC) Open

Rheem Furnace Pressure Switch Error Codes

The limit control in a Rheem furnace is a crucial safety feature. It monitors the temperature inside the furnace to prevent overheating. When the internal temperature of the furnace gets too high, the limit switch is triggered, shutting off the burner to prevent potential damage or a fire hazard. However, if there’s a problem with the limit control or if it’s getting triggered frequently, you might get specific error codes related to it.

44Low Pressure Switch Closed – Inducer OFF
45Low Pressure Switch Open – Inducer on High
46Low Pressure Switch Open – Inducer on Low
55High Pressure Switch Closed – Inducer OFF
57High Pressure Switch Open

Limit Switch Open:

  • Air Flow Restriction: One of the primary reasons for an open limit switch is restricted airflow. The heat isn’t dissipating fast enough, causing the furnace to overheat. Check your air filters to ensure they’re clean and all vents in your home are open and not blocked.
  • Blower Motor: If the motor isn’t working correctly, hot air won’t circulate out of the furnace. Listen for any unusual sounds and ensure it’s functioning and blowing air out of the vents.
  • Limit Switch Failure: The switch itself might be faulty. If you’ve ruled out other issues, it might be time to test or replace the limit switch.

Limit Switch Closed:

  • Continuous Blower: If the blower continuously runs even when the furnace isn’t heating, it might indicate that the limit switch is stuck in the closed position.
  • Manual Reset Required: Some Rheem furnaces have a manual reset limit switch. If it has been tripped, you’ll need to reset it manually. Locate the switch (often a red button on the switch) inside the furnace and press it to reset.
  • Switch Malfunction: A perpetually closed limit switch can also indicate a malfunction. If it remains closed even when the furnace is cool, you may need to replace the switch.

Limit Switch Did Not Open:

  • Calibration Issue: The limit switch may be out of calibration, causing it not to open even when it should.
  • False Reading: There might be a problem with the furnace’s sensor, giving a false reading.
  • Overheating Issues: Check if the furnace is genuinely overheating. If it is, you’ll need to address the root of the overheating problem. If not, the limit switch or related sensors might be faulty.

Venting Inspection: Over time, outdoor vents can get clogged with all sorts of debris—leaves, bird nests, or even snow. Make a quick inspection to ensure that nothing’s blocking these vents. Clear out any obstructions you find.

Pressure Switch Check: If your venting is clear and you’re still facing the error, the pressure switch might be malfunctioning. The switch ensures that there’s proper ventilation for safe operation. You can attempt to reset it, but if it’s faulty, it will need replacement. This is a task best left to HVAC professionals.

Rheem Furnace Blower Error Codes

60Blower Fault – Blower Remains Running
61Blower Fault – Blower Not Running
66Blower Overspeed Fault
68No Communications with Blower Motor

The blower is an essential component of your Rheem furnace, ensuring the proper distribution of warm air throughout your home. If something goes awry with the blower, your furnace will likely notify you with specific blower error codes.

Rheem Furnace Blower Motor Error

Let’s dive into what these codes mean and how you can potentially address them:

Blower Motor Overload:

  • Motor Inspection: The motor may be working harder than it should. This could be due to obstructions or an overburdened motor. Make sure nothing is obstructing the blower, like debris or foreign objects.
  • Electrical Check: Examine the connections to the motor and ensure they’re secure. Loose or frayed wires can cause an overload. If wires look compromised, it’s time to call in a technician.

Blower Motor Lockout:

  • Motor Reset: A locked-out blower motor might simply need a reset. Turn off your furnace at the breaker, wait a few minutes, then turn it back on. Sometimes, this can reset the system and clear the error.
  • Motor Health: If a reset doesn’t do the trick, the motor might be on its last legs. Motors can wear out over time and may need replacement, especially if they’re making unusual noises or if you notice a burnt smell.

Blower Running Non-stop:

  • Thermostat Check: The first step here is to ensure that your thermostat isn’t set to “fan on” mode. This setting causes the blower to run continuously. Switch it to “auto” mode so the fan only operates when heating the furnace.
  • Limit Switch Inspection: If your thermostat settings are correct and the blower still runs non-stop, the limit switch might be faulty. This switch can sometimes get stuck in the “open” position, causing the blower to run continuously. You might need to replace it, which is generally a job for a technician.

Blower Motor Failure:

  • Motor Check: This indicates that the motor isn’t running as expected. Listen for any unusual sounds from the motor. Grinding or whirring sounds can be a tell-tale sign of a problem.
  • Capacitor Examination: The capacitor gives the motor the initial boost to start. A faulty capacitor could prevent the motor from starting. If you’re comfortable and knowledgeable, you can test the capacitor with a multimeter. If it’s faulty, it’ll need replacement. If you’re unsure, it’s best to call in a professional.

Rheem Furnace Gas Valve Error Codes

The gas valve is a critical component of your Rheem furnace. It’s responsible for controlling the flow of gas to the burner, ensuring proper ignition and consistent heating. When there’s an issue with the gas valve, the furnace will alert you with specific error codes. Let’s explore what these codes signify and how to address them:

77No Communications with Gas Valve
78Gas Valve Servo Fault

Electrical Inspection: Check the wiring leading to the gas valve. Over time, wires can become loose or corroded. Ensure they’re secure and in good condition. If you spot any damage, it’s time to replace them or consult a technician.

Valve Check: Ensure the gas valve is in the ON position. Occasionally, it may get accidentally turned off during maintenance or other activities. A valve that opens too quickly might be showing signs of wear and tear. Inspect it for any visible damages or signs of deterioration.

In dealing with gas appliances, it’s crucial to prioritize safety. If you smell gas or suspect a leak, shut off the gas supply immediately and evacuate your home. Always consult with professionals when you’re unsure about any troubleshooting steps, especially when dealing with gas components.

Another Misc. Error Codes

26Line and Neutral Reversed
82Supply Air Temp / Sensor Fault
93Internal Fault / Control Fault

If, after all these checks and fixes, you’re still encountering errors, it’s time to call a technician. Your Rheem furnace is a complex machine, and sometimes, the expertise of a professional is needed to get it back in tip-top shape.

Rheem Furnace Common Problems and Possible Solution

This chapter summarizes the most common problems you could encounter with your Rheem furnace. If you are unable to diagnose and solve the problem with the information below, contact an experienced and certified HVAC technician for certain complex problems.

ProblemsPossible Solutions
Flame Sensor ProblemIf the flame sensor is dirty, clean the sensor. If faulty or broken, replace the flame sensor. Click Here for the detailed guide to clean/replace furnace flame sensor.
Circuit Breaker/FuseTry resetting your furnace’s circuit breaker. Click Here for the detailed guide tp reset your furnace.
IgniterCheck the furnace igniter for cracks, if it is then replace the igniter. If it isn’t cracked, use a multimeter to test for continuity. Click Here for the detailed guide to check the furnace igniter.
Blower MotorCheck the blower motor. If it isn’t running, the motor has likely broken. If the motor runs but air doesn’t move, the connecting belt may the problem. Click Here for the detailed blower motor troubleshooting guide.
Internal FaultCheck the furnace control board. Click Here for the detailed guide to troubleshooting funace control board.

Many modern furnaces have an LED light that will either be flashing or just showing some codes. Even though you may be able to interpret the Rheem furnace error codes, furnace repairs are generally best left to the professionals.

Listen, I’m all about DIY, but there are moments when it’s best to let the experts step in. If you’ve tried troubleshooting and the errors persist, or if your furnace repeatedly shuts down, give a professional a call. Remember, safety first!

Rheem furnaces are a staple in many homes, and while they’re designed for durability, occasional error codes aren’t out of the ordinary. The key is understanding what these codes mean and taking the right steps to troubleshoot. And if in doubt, don’t hesitate to bring in the pros!

mas broto avatar

Mas Broto

Have been in the heating and air conditioning (HVAC) industry for over 20 years. He is person that will grow and thrive to learn more about the HVAC industry throughout his career. Mas Broto is also a blogger, who's dedicated to bringing you the best knowledge to get ahead in the game of life.

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