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Rheem Furnace Troubleshooting & Repairs

At Fire & Ice, we are a proud Rheem dealer and want homeowners to be equipped with information on troubleshooting and repairing Rheem furnaces.

Rheem Furnace Troubleshooting & Repairs

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Fire & Ice Team


April 6th, 2023

Our residential heating and cooling systems are one of the most vital pieces of comfort technology within our homes. It keeps our homes cool on a hot summer’s day or warm on a cold winter night, but what happens when your furnace breaks down? 

Rheem furnaces are well-known for being reliable, tested, trusted, and tough; however, like with any piece of technology, they can break down. Keeping in mind that technology is our friend but not always our best friend, you could try troubleshooting the problem yourself.

However, you should note that our residential HVAC system is not only one of the most vital pieces of your home’s overall comfort but also one of the most expensive. 

At Fire and Ice, we have troubleshooted, diagnosed, repaired, replaced, and installed hundreds of Rheem furnaces throughout the Columbus metropolitan area.

By the end of this article, we hope that you know why your furnace isn’t working, the steps to take, and when to call the professionals.

Let’s begin

Common Rheem Furnace Problems

To understand why your Rheem furnace is having problems, you must first know the most common reasons for a furnace malfunctioning. In this section, we will cover typical furnace issues along with troubleshooting tips directly from Rheem.

Is Your Rheem Furnace Not Generating Heat?

First, you’ll want to ensure that your thermostat is set correctly. When utilizing your HVAC system, it should be “on” and on the “auto” setting. If you keep the “fan” setting on, your furnace will continue to blow out air that hasn’t gone through a heating cycle.  

When this happens, you will get cold or “unconditioned” air coming through your vents, which is when homeowners begin to worry that their furnaces may be on the fritz.

If you’ve checked your thermostat settings and they are correct, the next thing you can do is check your furnace filter. Did you know that a dirty furnace filter is the most common reason for furnace problems?

Dirty furnace filters can cause a number of issues, including but not limited to the following:

  • Restricted airflow
  • Higher monthly energy bills
  • Lower energy efficiency
  • Uneven temperatures
  • An overheated furnace/breakdown

If you’ve checked your furnace filter and it’s not clogged, or you’ve changed it and still have furnace issues, then you should check all of the vents and registers in your home. Any visible obstructions, like furniture, a clothes pile, boxes, dog crates, etc., can also cause improper airflow, which can be why your furnace isn’t generating heat.

If all of your vents are free from visible obstructions, one may be inside your ductwork. If this is the case, you’ll want to call an HVAC contractor, like Fire and Ice, to complete an air duct cleaning. Investing in air duct cleaning has several benefits, such as:

     A cleaner home

     Minimized allergy symptoms and nasal irritation

     Improved HVAC airflow

     Removal of stubborn smells and odors

     A longer lifespan for your HVAC equipment

You can also take a look at our Air Duct Cleaning Homepage to learn more about our air duct cleaning process. It covers indoor air quality benefits, when to invest in an air duct cleaning, frequently asked questions, and the additional air duct cleaning services we provide.

Other things to check:

     The gas valve (if applicable)

     Furnace pilot light (generally, furnaces over 20+ years old will have a pilot light, which you will have to relight manually)

     Burners (dirty burners can prevent ignition of your pilot light)

However, if you have gone through all of these Rheem furnace checks and your whole home heating system is still not generating warm air, it’s time to call the experts.

Is Your Rheem Furnace Short Cycling?

In the HVAC world, short cycling refers to when your furnace turns on and off more frequently than it should. Not only will this rob you of warmth, but it also doesn’t allow your home to reach your optimal comfort level.

Below are the most common reasons for an HVAC system short cycling:

1. Dirty Furnace Filter - I know we mentioned this above, but this shows you how important a clean air filter is.  However, if you don’t know how to change your filter or if you can’t change it on your own, consider investing in one of our maintenance plans.

As a general rule of thumb, your air filter should be changed or checked at least once a month (depending on your HVAC system/filter). Investing in one of our maintenance agreements will guarantee at least two filter changes a year, which is better than none.

Regular maintenance will improve your system's energy efficiency, prolong its lifespan, keep your warranties intact, catch potential problems before they become detrimental, and ensure your HVAC system is ready for the next season.

Buy Your Filter


2. Thermostat Malfunction- If your thermostat is set on the wrong setting or not properly placed, it can cause your HVAC system to short cycle. Depending on the complexity of your thermostat, you can open it and replace the batteries.

However, most smart thermostats connect directly to an electrical wire, so proceed with caution!

Also, if your thermostat is located on an exterior wall, near a register/vent, near any windows or doors, or in direct sunlight, consider moving your thermostat to a more optimal location.

Related Content: Does the Placement of Your Thermostat Actually Matter?

3. Air Leaks - This is when your conditioned air gets distributed throughout your home but leaks through any windows, doors, or holes/cracks in your ductwork before reaching its final destination.

In fact, according to
AeroSeal, a majority of residential homes have between 10% and 25% conditioned air leakage. If you have air leaks throughout your ductwork, it can cause various other whole home problems, such as

     Hot and cold spots

     A build-up of dirt, dust, debris, and common airborne allergens

     High utility bills/low energy efficiency

In this instance, you could buy caulking to seal around your windows and doors at your local hardware store. If the problem persists, it could be due to your ductwork. If so, you'll want to call your trusted HVAC contractor to ensure your ductwork is properly sealed.

4. Issues With Parts - If you've checked all of the above and still have Rheem furnace problems, it could be due to a part malfunction. Like any piece of machinery, parts inside your furnace are exposed to wear and tear. Common parts problems include the furnace blower, the flue, and the flame sensor.

5. Under-Sized or Oversized HVAC System - More often than not, one of the biggest culprits of a malfunctioning Rheem furnace is due to improper sizing. According to the EPA, almost half of all HVAC systems are improperly sized.

You may wonder why so many HVAC systems are undersized or oversized; in fact, The biggest factor contributing to an improperly sized HVAC system is that a
Manual J Load Calculation was never performed.

Unfortunately, many HVAC contractors cut corners and don’t perform a Manual J Load Calculation, even though
ACCA (Air Conditioning Contractors of America) requires it. This is shocking when you consider that this calculation is vital for any successful HVAC installation.

The Manual J Load Calculation considers several factors to ensure a properly sized, energy-efficient heating and cooling system, such as:

  • Your home's total square footage
  • How many people live in the home
  • How many windows your home has
  • The type of windows (single-pane or double-pane, etc.)
  • The number of doors your home has
  •      Height of the ceiling
  •      If your home has a basement or if it is on a concrete slab
  •      Plus more

 Also Read: What Do Windows Have to Do With It? All About Windows and Your HVAC?

It's also important to note that the HVAC contractor you hire to complete your installation is more important than your chosen HVAC brand.

If you’ve checked all the above and your HVAC system is still short cycling, contacting a professional is best. They can diagnose, repair, replace, or install a new HVAC system.

Is Your Rheem Furnace Constantly Running?

If your HVAC system is constantly running, it could be for various issues. First, you should make sure your thermostat is set to the correct setting. If you don’t want your HVAC system to run consistently, you’ll want to check that it is on “heat” and “auto.”

Remember that if your thermostat is set to “fan,” it will continuously run to move air throughout the home. If your thermostat is set to “on,” you can flip the switch to “auto,” which should correct your problem.  

If your thermostat is set to “auto,” the next thing to check is your furnace filter. As mentioned before, a dirty air filter can cause an array of furnace problems, including restricted airflow, lower energy efficiency, and even cause your HVAC system to run consistently.

Also, at this point, you should check your air ducts for any leaks or blockages. If your warm-conditioned air leaks, your furnace may have trouble reaching your desired temperature, thus causing your furnace to run constantly.

If you have checked the above issues and your Rheem furnace is still continually running, you can check your limit switch. If this part of your system is broken or damaged, it can result in an overworked furnace. If you suspect this is the issue, contact your local and trusted HVAC contractor to schedule a limit switch repair.

Rheem Furnace: Error Codes, Problems, & Solutions

Your furnace can give you signs and signals as to what the problem may be. If your furnace is newer and has an LED display, it may give you a code.

We're not all HVAC professionals, so check out the table we created for Rheem furnace troubleshooting issues to help our customers understand the different codes, a description, and the next steps.



Next Steps


Furnace is in “standby mode”

N/A, This is normal operation


Dehumidifier is “on”

N/A, This is normal operation


“Defrost Mode” is “on”

N/A, This is normal operation


Fan is set to “on”

N/A, This is normal operation

H (Blinking)

Your furnace is calibrating

N/A, This is normal operation


Heat is “on”

N/A, This is normal operation


No data to share

Your furnace is not communicating with your thermostat


1-hr system lockout

Contact your trusted HVAC professional


Ignition failure

Check the gas valve connection, flame sensor, and your gas supply


Low pilot light flame

Check the gas valve connection, flame sensor, and your gas supply


Blown out pilot light flame

Check the gas valve connection, flame sensor, and your gas supply


Accidental flame

Call your trusted HVAC professional ASAP


Open main limit

Your furnace may be overheating. Look for any blockages or improper ventilation


Open heat assist

Your furnace may be overheating. Look for any blockages or incorrect ventilation


Reversed line and neutral

An electrical problem. Contact your trusted electrical company


Open manual reset limit

Check the temperature of your furnace, if correct reset your limit switch


Closed low-pressure switch; inducer motor is “off”

Inspect the inducer motor to prevent dangerous backdrafts into your home


Open low-pressure switch; inducer motor is “on”

Your air intake may be obstructed


Open low-pressure switch; inducer motor is set to “low”

Your air intake may be obstructed




Closed high-pressure switch; inducer motor is off


Inspect the inducer motor to prevent dangerous backdrafts in your home


Open high-pressure switch

Obstructed airflow


Blower fault; blower is running

Inspect the blower compartment  for possible issues


Blower fault; blower is not running

Inspect blower motor for possible issues


Blower overspeed fault

Inspect the blower compartment for possible issues


Invalid communication with blower motor

Inspect blower motor for possible issues


Invalid communication with gas valve

Inspect gas valve for possible issues


Gas valve service fault

Inspect gas valve for possible issues


Supply air temperature fault

Inspect the air temperature sensor for possible problems


Internal or control fault

Inspect the air temperature sensor for possible problems

Rheem Furnace Repair, Replacement, and Installation

If you’ve checked, tightened, inspected, and troubleshooted all of the above, then it’s time to call your HVAC partner. At Fire & Ice, we understand that your furnace is directly related to your overall comfort, and you deserve to be comfortable.

So, whether you're in the market for an HVAC repair, replacement, installation, emergency services, or having an air conditioner, heat pump, or furnace problem, you've come to the right place! If you’re in the Columbus, OH, area, we’d love to help you with your system.

Call or click below to begin your HVAC journey with Fire & Ice today!

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