How To Fix It

7 Most Common Rheem Furnace Problems, Made Easy

When your furnace stops working, it can be an uncomfortable feeling.  The discomfort of being without heat in your home can be more than just an inconvenience. 

The thought of massive repair bills or even having to replace your Rheem furnace can be chilling.  No pun intended.  

Before you start shivering at the thought of calling the Rheem repair technician, there are some simple diagnostic steps you can take. 

Often the cause of Rheem furnace problems are minor and easily repaired by a homeowner. Some of the most common problems with Rheem furnaces include:

  • No heat or insufficient heat
  • Frequent cycling of the furnace on and off
  • A blower that runs constantly
  • A noisy furnace that rattles of bangs
  • A pilot light that won’t stay lit
  • An electronic Igniter that won’t spark
  • Thermostat problems

No Heat or Insufficient Heat – Rheem Furnace Problems That Aren’t Cool To Have

If no warm air or only a little warm air is coming from the vents in your home. Begin by checking that your furnace is working. 

Turn the thermostat up and listen for the furnace to start.  Carefully check that the furnace fan is working.

You may need to remove the service panel on the furnace to make this check.  Be careful.  There are electrical circuits in this area that can be a potential shock hazard. 

With the service panel off, the burners in the heat exchanger should be visible.  The flames should be burning with consistent blue color and the fan below the heat exchanger should be running.

furnace gas burners

If everything seems to be working and there is still little or no warm air coming from the vents, you must investigate further to identify the problem.

Check the Air Filter – Have you Changed it Recently?

Changing the air filter in your Rheem heater is one of those maintenance issues that we often overlook. 

A dirty filter is a usual suspect when the Rheem heater stops producing enough warm air for the home.  

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Rheem furnace problems: filter needs replaced

Follow the Rheem user’s manual that came with your heater and replace the old filter with a fresh filter of the correct size. 

A clean filter will often increase airflow through the heater and into your home, solving your problem.

Duct Work Problems – No Place for the Warm Air to Go

If the filter on your Rheem furnace is clean and everything else is working correctly, a problem in the ductwork that carries warm air to your home may be the culprit. 

new construction furnace and ductwork in attic
Image Credit: GreenBuildingAdvisor

Collapsed ductwork is a rare condition but can happen.  Collapsed ductwork above your heater results from someone falling or leaning on the ductwork while working in the attic. 

To diagnose this problem, you must inspect the ductwork in the attic.  Take care when working in the attic to only step on the ceiling joists. 

You don’t want to do further damage to your home. If you find collapsed or unsealed ductwork, repair or replace the damaged sections.  

Frequent Cycling – The Short Cycle Symptom

Under some circumstances, short cycling in your Rheem furnace is normal. 

During periods of extremely cold weather, your Rheem furnace may need to operate frequently to keep your home at a comfortable temperature.

However, if your Rheem furnace cycles on and off frequently during milder periods of cold weather, it indicates other problems.  

These other problems often relate to a faulty thermostat or something as simple as a dirty filter

Suppose your Rheem furnace continues to short cycle after a filter change.

In that case, it will probably be necessary for you to consult with a qualified Rheem service technician to diagnose the problem further.

The Blower On my Rheem Furnace Runs Constantly

Several problems can result in the blower fan on your Rheem furnace running constantly. 

Check for these issues on your Rheem furnace when the blower fan runs constantly.

Thermostat FAN Setting.  Is it in the ON Position?

Check your thermostat first and ensure that the FAN setting is in the automatic position and not the ON position. 

These settings can get changed accidentally.  An incorrect fan switch setting is the most common cause of a Rheem furnace blower operating continually.

A Faulty Fan Limit Switch

Another possible cause for the blower fan constantly running in your Rheem furnace is a faulty fan limit control switch. 

If the switch has a reset, reset the switch.  If the switch is faulty, replace the switch.  

furnace fan limit switch

If your furnace is a newer model, the fan limit control switch may be part of the control board. 

In this instance, consult a qualified Rheem furnace technician about remedying the problem.

A Noisy Furnace – A Rheem Furnace that Disturbs the Peace

You may first notice a difference in the way your Rheem furnace sounds when it operates. 

Even the slightest change in the noises your furnace produces bears investigation. 

When a Rheem furnace begins to make noises, the usual suspect is the blower fan and the motor that drives it.    

The fan motor may have a problem or the bearings on the fan itself could be about to fail. 

Noises coming from your furnace is usually not a time to try and diagnose and fix a problem. 

Removing the fan motor and fan requires working with electrical and mechanical systems. 

A trained and qualified Rheem furnace technician has the knowledge and tools to perform this service safely and expertly.

Keeping the Fires Lit on Your Rheem Furnace

Older Rheem furnaces have pilot lights the burn continuously. 

If you cannot get the pilot light on your Rheem furnace to light and stay lit, the most common problem is a bad thermocouple. 

The thermocouple tells the furnace controller that the pilot light is working. 

If the pilot light is not working, the gas control valve will not open and you won’t get any heat.

burnt furnace thermocouple

The thermocouple should be mounted so that the pilot light’s flame heats the end of the thermocouple.  The heat from the pilot light generates a small electrical current. 

If the thermocouple is not in the flame of the pilot light, it won’t work.  Make sure the thermocouple and pilot light are properly aligned.

If the furnace still won’t work, the thermocouple is probably bad.   You can test the thermocouple using a multi-meter. 

If the thermocouple doesn’t produce a small electrical current when the pilot light is burning, replace the thermocouple.

furnace thermocouple

No Spark No Heat – Igniter Problems on your Rheem Furnace

Newer Rheem furnaces use an igniter rather than a pilot light.   Igniters are both safer and more economical than pilot lights. 

You can easily check the igniter on your Rheem furnace by removing the service panel and watching the igniter when the furnace starts to cycle.

If the igniter is working, you can see a small spark pass from the end of the igniter to the burner. 

You may also hear the sharp click as the igniter is activated.  If there is no spark or click, you must check the igniter.  

If the igniter proves to be working and the burners still won’t light, you have a more serious problem that may be related to the control board on your Rheem furnace. 

If an issue with the control board is suspected, call your Rheem service technician for help.

Check the Thermostat

Many newer thermostats require batteries to operate correctly.  If you have a newer thermostat, especially a programmable model, check the batteries in the thermostat. 

It is a good practice to change the batteries in your thermostat once a year, just like the batteries in your smoke detector.  

Communicating with your Furnace – Rheem Error Codes

Many newer Rheem furnaces will display error codes when one of the furnace systems has a fault. 

The small LED display on which the error codes display is usually on the controller board.  The service panel for the furnace must cover the display.

Your user manual will have the codes with a short description of the problem. 

If you don’t have your user manual, here is a chart showing some of the most common error codes seen on Rheem furnaces

Error CodeDescription
10A one-hour lockout has occurred
11Burner Ignition failed
12Low Flame 
13Flame lost
14Unexpected flame
20Twinning failure
22High limit detected
26Line and neutral reversed
33Roll-Out Switch problem detected
55Pressure switch fault
58Water on condensation problem
61Blower malfunction
93Control board problem

Further diagnosis is usually required when one of the error codes is displayed. 

A trained Rheem technician is trained in using these error codes to identify and repair the associated problem.

Keeping the Heat Flowing

If your Rheem furnace is not performing up to expectations or if it just doesn’t work at all, before you pay for a service call, investigate these seven common problems. 

You may find that a quick trip to the appliance parts store and a little hands-on work can get your Rheem furnace back to full operation.  Good luck.

2 thoughts on “7 Most Common Rheem Furnace Problems, Made Easy”

  1. Several pops on my heating system before the click turns the heat on. Usually at 3-4AM This is an intermittant problem. It wakes us up at night. I have had the technician out several times and when he turns the thermostat on everything works. I do get heat once the popping stops. My unit is still under warranty but I was told if they replace and the unit is not faulty then I would be charged Please advise how to proceed. Sun city Mechanical was the original installer and I have paid several service calls to tell me nothing is wrong.

    • Intermittent problems are not easy to figure out. Did you try to call a different service company? Maybe call several of them and explain an issue. For me it sounds like a problem with the ignition. maybe some dirt on the burner or there is a hole in the heat exchanger

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