Rheem Furnace Error Codes

Wondering what your Rheem furnace is trying to tell you? Here is a detailed explanation of all the error codes that might appear on the unit’s display.

How Do You Read a Rheem Furnace Error Code?

Rheem furnaces come with an advanced diagnostic display that you can consult, whenever something goes wrong.

These units don’t use only flashing LED light sequences, but the furnace can blink a few times with a two-second pause (you’ll find out what these light codes mean below).

In the majority of cases, the display will give you an extremely simple code to tell you what’s going on.

You’ve got nothing to worry about if you see these indications:

  • 0 – your furnace is on standby.
  • H – the heating is on. 

Rheem Furnace Error Codes

Error Code 10

This is a warning code. It might result in a one-hour lockout.

It might be because the unit’s fan is not creating enough ventilation.

  • Check if the fins of the heat exchanger have been blocked.
  • Clean the air filter.
  • Remove any obstructions (pay extra attention to the vents outside the house and the valve at the top of the heat exchanger). 

Error Code 11

The ignition has failed. 

  • Make sure that your thermostat is set to ‘heat’ and that the temperature in the house is lower than the set temperature.
  • Check if the gas is turned on. After that, check the gas supply to the actual furnace.
  • The ignition sensor might be dirty or faulty. When cleaning the sensor, be careful, as the component can easily break.

Error Code 12

Low flame (flame failure).

The problem might, once again, be with the flame sensor.

In the majority of cases, the component is not broken, it had just become dirty from all the carbon buildup.

To clean the flame sensor, first, make sure that you have turned the furnace off. Pull the wire off the sensor, remove the screws, and gently wipe the component with steel wool or sandpaper.

Tip: the flame sensor is usually located in the direct path of the burner, it is a metal rod with a wire attached to it. 

Error Code 13

The flame was lost.

Yet another error that can be caused by a dirty flame sensor.

The problem might also be with a tripping pressure switch or a broken thermocouple – a safety component that measures the temperature of the flame. 

Error Code 14

Unexpected flame.

A faulty flame sensor might be to blame.

Do bear in mind that the visible flame in your furnace should have a bluish-green color. If the flame is yellow or orange, then there is a serious issue with the unit and you need to call a professional. 

Error Code 20

A twinning fault. 

It might mean that there is a failure to communicate between the control boards. The problem may also be with the thermostat or the thermostat wiring. 

Error Code 22

An issue with the high limit switch. 

The switch tends to trip whenever there is a problem with the airflow in the system. 

The most common cause for that is a dirty air filter

To ensure proper air movement in the system, you can open all vents and registers and check if the flow is relatively stable throughout all the openings. 

Remember that the actual switch can be defective. It can wear out over the course of time, especially if it has been tripping a lot. 

Error Code 26

A reverse polarity issue. 

Your furnace has hot and neutral wires that have to be connected to a specific connection. This error can occur if the hot and neutral wires get flipped around.

Error Code 33

A problem with the rollout switch. 

The safety device detects the presence of flame rollout (when burner flames come ‘backward’) and shuts off the gas valve.

There are a few things that can be wrong with the switch:

  • The buildup of soot.
  • Blocked flue.
  • A bad flame sensor switch.
  • A blocked tube in the heat exchanger.
  • A cracked heat exchanger. 

Error Code 55 ; 57

An issue with the pressure switch.

When the furnace is operating correctly, there should be a degree of negative pressure in the system. In such a case, the pressure switch is going to remain open. 

However, if the pressure is not correct, the switch will close the circuit and shut the furnace down. 

The cause might be:

  • Restricted intake air vent or combustion air vent
  • Clogged condensate drainage
  • Failure of the draft inducer motor

Error Code 58 ; 59

Water and/or condensation problem.

If you have a high-efficiency condensing unit, then it looks like the condensation drain or tubing may be clogged. Or there is a problem with the condensate pump.

Bear in mind that your furnace has to be properly serviced, in order for it to be able to drain the water that condensates.

Read: How Much Does It Cost To Move A Furnace And Water Heater?

Error Code 61

Issues with the blower.

Check the thermostat setting and the filters. If everything seems to be ok, then the problem might be with the blower’s drive belt.

Inspect the belt, it can crack or get worn down.

Error Code 93

Issues with the control.

The circuit or control board can fail for quite a few reasons.

  • Clogged filters.
  • Dirty fuse (also, do make sure that the fuse is not too small for your furnace)
  • Loose wiring (the wires might become loose over time due to vibration)

Read: Why Does Home Thermostat Say HEAT ON But There Is No Heat?

What Are the Codes for the Lights on a Rheem Furnace?

Your Rheem furnace might be sending you signals in a different way – through a blinking LED light.

One Blink with a Two-Second Pause

If you see a blink and then another blink in 2 seconds, it means that your furnace is in lockout mode that is going to last for about an hour.

It is a safety measure that can be caused by quite a few different things. 

During this hour, you won’t be able to turn the furnace on and it won’t be working. As a result, the system will have enough time to cool down.

Hopefully, the problem will go away as soon as the unit has a chance to ‘rest’.

You can try to turn the furnace off and then reset the system – this might end the lockout, but it won’t fix the root cause of the problem. So, ideally, you should invite an expert to have a look at your system.

Warning! The lockout can be caused by a gas leak. If you smell gas, turn the unit off, leave the house, and call a professional.

Read: Why Gas Furnace Is Overheating?

Two Blinks with a Two-Second Pause

This signal means that the pressure switch is open.

The component is another safety device that is normally open but closes when negative pressure is required (when the furnace is turned on).

If the pressure switch doesn’t close, the furnace is going to shut itself down.

Here are a few reasons why your pressure switch might not be closing:

  • An obstruction in the flue
  • The pressure switch hose is damaged
  • The hose has water in it
  • The port on the collection chamber is clogged
  • The diaphragm is stuck or ruptured

Three/Four Blinks with a Two-Second Pause

It looks like the limit switch is closed (though it should be open).

In a nutshell, without this switch, your unit wouldn’t be able to regulate the temperature of the air in conjunction with the thermostat. 

As soon as the furnace heats up, the switch will close and turn on the blowers. When your house reaches the desired temperature, the burners turn off, but the limit switch stays open and keeps the blowers running to get rid of all the heated air.

The actual switch might be stuck or the tubing that is attached to this component is blocked.

Better leave this job to a professional, if you don’t know how to use a multimeter and don’t have a basic understanding of wiring. 

The LED Blinked Five Times

You might see such an LED code, only if you are a proud owner of a twinned furnace.

Not all units have such capabilities. The furnaces manufactured by Rheem that can be twinned are used in one house together on the same thermostat and ductwork. 

Homeowners decide to go for such an option, in case a single unit won’t have enough heating capabilities to keep the whole house warm.

The unit will start to blink if there is a fault with the setup.