Rheem Furnace Won’t Stay On – What Could Be Wrong?

Were you in the middle of a cold winter, and your Rheem furnace kept shutting down? Or maybe it will turn on for a few minutes then turn off? We've done the research for you to find out why it is acting this way and can explain it for you.

Several reasons could make your Rheem furnace constantly shut down. This problem could be caused by:

  • Low airflow
  • Faulty Thermostat
  • Dirty Flame Sensor
  • Bad blower motor
  • Clogged Flue Pipe
  • Over-sized furnace

Whew! That’s a lot of reasons why your Rheem furnace potentially keeps shutting down! But don’t feel overwhelmed just yet because we discuss each of these causes in detail in the succeeding sections. Read on!

Plumber fixing gas furnace, Rheem Furnace Won't Stay On - What Could Be Wrong?

Rheem furnace won’t stay on

Short cycling is when your furnace stays on for a brief period, then turns off and turns back on again. There are several reasons why your Rheem furnace does not stay on. And there are unique ways to address each one of them.

Weak airflow

If your furnace has weak airflow, it will not be able to release the heat that it produces into the air inside your house. In effect, this traps some of the heat inside your furnace, and this trapped heat accumulates until it overheats your furnace and shuts down.

Weak airflow can be caused by any of the following issues, or a combination of them:

Closed or blocked air supply vents

The heat exchanger is dependent on the flow and exchange of air. If there is insufficient flow of air, there will also be an insufficient transfer of heat. And this can lead to overheating inside your furnace. Once it overheats, it will shut itself down. Clearing or opening the blocked vents will help resolve this issue.

Dirty air filters

Dirty air filters can limit the flow of air inside your Rheem furnace, and this can cause it to overheat. Filters should be replaced every 90 days. If you have pets in the house, the air filters should be replaced every 60 days instead. If you have allergies, the air filters should be replaced more often.

Dirty blower wheel

Blower wheels push the air, and if the blower wheel is dirty, it will not work as efficiently as before. You can slow down the buildup of dirt on your blower wheel by regularly changing the air filters. If this issue gets worse, the damage it can cause can be expensive to repair. Clean the blower wheel or have a professional check and clean it for you.

Faulty Thermostat

The thermostat monitors the air temperature and sends a signal to your furnace if the temperature gets too low. The signal turns on the furnace to produce more heat. If the temperature is too high, the thermostat sends a signal to the furnace to turn off.

If the thermostat cannot detect the right temperature, it will be sending the wrong signal to the furnace. There are three reasons why your thermostat might be having a problem detecting the right temperature:


Most thermostats have batteries. If the battery is low, the thermostat will keep shutting down and turning back on. A thermostat with low batteries means that the temperature sensors are not getting the right amount of power to function properly. Replacing the batteries with fresh ones can help fix this issue.

Bad location

A thermostat that is installed in an inappropriate or bad location can cause the furnace to keep shutting down and turning back on. An inappropriate location is one where the thermostat is exposed to sources of heat.

The thermostat will not be able to provide an accurate reading of the temperature if it is exposed directly to sunlight. The same thing will happen if the thermostat is installed near a location with a naturally higher temperature than the rest of the house like the kitchen or the bathroom.

Relocating the thermostat to a more appropriate location will address this issue. Read our article about relocating thermostats here.

Faulty wiring

An old thermostat that has been with you for a long time can have old and faulty wiring. A thermostat with faulty wiring will be unable to send the correct signals to the furnace to function properly. Have a professional verify the issue and rewire your thermostat for you to resolve this problem.

Dirty Flame Sensor

Flame sensors detect if there is a flame inside the furnace. It will automatically shut down the gas valve if it doesn’t detect a flame. The Rheem furnace will turn off afterward. This error can happen if the flame sensor is dirty or corroded. Clean the flame sensor and check if this will resolve the issue. If not, it will have to be replaced.

You can purchase a replacement flame sensor for Rheem furnaces. Use this link to see this part on Amazon.

Bad blower motor

The blower motor is responsible for circulating warm air throughout your house. It is rare, but it is still possible for your furnace to be on while the blower motor is off. If this happens, the heat generated by your furnace will stay inside your Rheem furnace, and this will cause it to overheat.

One way to check this issue is to hold your hand over one of the heat vents. If there is no air coming out from it, then the blower motor might have stopped working. Have a professional verify and replace the motor for you.

Clogged Flue Pipe

The flue pipe, also known as the exhaust vent, is where unwanted gases exit the furnace. This pipe is usually located on your roof. It can be blocked or clogged by dirt, leaves, sticks, bird’s nests, and other debris. Clearing the debris should resolve this issue.

Oversized furnace

An oversized furnace can also cause short cycling. If the furnace is too big, it will be able to warm up your house too fast, and then it will shut down.

Once the temperature drops, your Rheem furnace will turn back on, and the cycle goes on once more. This usually happens when sales representatives sell you equipment that you do not need so that they can clear off inventories. Unfortunately, replacing your Rheem furnace is the only way to resolve this.

Other Common Rheem Furnace problems

The sections below list other common problems with the Rheem furnace. We included simple troubleshooting steps to help you isolate and fix the problem.

No heat or too little heat from the Rheem furnace

Turn up the thermostat and check if your Rheem furnace has started up. After a few minutes, check for warm air coming out of the vents.

If there is little or no air coming out of the vents and your air filter is clean or new (we covered air filters above), then the problem could be in the ductworks. A collapsed ductwork is rare, but it can still happen. It can be caused by someone leaning on the ductwork or something falling on it while working in the attic.

Carefully check the ductwork in your attic. Once you find collapsed or unsealed ductwork, seal it or replace the damaged sections.

The blower is constantly running

Several issues can make the blower on your Rheem furnace keep running. Check the following possible causes to fix the issue.

Thermostat setting

Check your thermostat and make sure that the fan setting is not set to the “on” position. If it is, change the setting to “automatic” instead. This setting can easily get changed accidentally and is one of the most common reasons why the blower on the Rheem furnace is constantly running.

Faulty fan limit control switch

A bad fan limit control switch can cause the blower to be constantly on.

Older models have a reset button on the fan limit control switch, and pressing this button will resolve the problem. However, newer models have this switch integrated into the control board. If this is the case, have a professional check and fix the issue for you.

Rheem error codes

Newer Rheem furnaces communicate problems in the system by displaying error codes.

There is a small LED display on the control board that displays the error code. Remove the service panel of the furnace to access this display. According to the The Daily Thrive, Rheem furnaces do not use blinking LED lights to communicate possible errors within their system.

A safety reminder before removing the service panel: make sure that the furnace is turned off and that the panel is not too hot before you try to remove it. The Rheem furnace user manual should have a table of the codes and what they mean. Most models have a copy of the same table on a sticker inside the panel cover.

Further troubleshooting is needed when you receive an error code from your Rheem furnace. Have a professional check the code and fix the issue for you.


There are several reasons when a Rheem furnace will not stay on. Going through each one is the first step to fixing the problem.

Having trouble with your furnace, but don't have a Rheem? Check out: "How To Reset A Carrier Furnace."


Share this article

Leave a Reply

Your email address will not be published. Required fields are marked *