Carrier Furnace Error Codes – How To Understand Them

What do Carrier Furnace error codes mean? Don’t worry, we’ve got you covered. Starting with a flashing LED light and ending with the mysterious two-digit codes – after reading this guide, you’ll know exactly what your furnace is trying to tell you.

Also, at the bottom of this article, we’ll show you how to access the diagnostic mode of a Carrier Infinity thermostat.

How Do You Read Carrier Furnace Error Codes?

If there is ever a malfunction in the system, your Carrier furnace is going to alert you about it.

This is done with the help of a two-digit code. The first number indicates the number of flashes made by the yellow light, while the second – the flashes made by the green light.

The green light usually indicates that everything is working properly. For example, a rapidly flashing green light might mean that the blower system is working (which means that the furnace is providing heat to the house at the moment).

Carrier furnace error codes flashing lights

A slowly flashing green light indicates that the system is on, but a request for heat hasn’t been made.

A yellow light would mean that there is a problem of some sort in the system that requires a closer inspection. 

If your furnace has no light, it means that either the unit is completely off or that it is not receiving any electrical power. Check the circuit breaker(s) at the house electrical panel, and also the breaker on the furnace.

If you have a gas furnace, check the disconnect switch on or near your furnace. It looks like a regular light switch. Make sure it’s in the ON position.

Read: Why Furnace Is Not Blowing Hot Air?

Carrier Furnace Error Codes – Rapid LED Flashing

If you ever notice rapid LED flashing that means that the line voltage polarity is reversed.

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Blinking LED light on Carrier furnace

In a nutshell, the neutral wire in the system is connected to where the hot wire has to be. The main problem with an outlet that has reversed polarity is that electricity will always be flowing out of the outlet, even if your furnace is turned off.

Warning! Reversed polarity presents an extremely serious shock risk.

You should check the polarity at the unit and make sure that it is correct. However, if you do not feel comfortable working with electricity and wires, then leave the job to a professional.

A furnace can work on reversed polarity for a long period of time, but, at one point, it might start having an issue with it.

Such a situation might have also occurred after someone made changes to the wiring. 

Carrier Furnace Error Codes List

Carrier Error CodeWhat’s wrong?What should you do?
Code 1-1No previous codeThe stored status codes are erased after 72 hours or when power to the system is interrupted.
Code 1-2Blower on after startup.This means that the blower starts pushing the air out of the system before it becomes heated.Normally, the blower fan should start working only about 1.5-3 minutes after the thermostat calls for heat.Ensure that the thermostat’s fan setting is at ‘on’, not ‘auto’.You might have accidentally connected the fan wire to the heat terminal or the heat wire.Check the back of the thermostat – it has to be set to ‘gas heat’ if you have a gas furnace.
Code 1-3Limit (often, auto reset) or flame rollout (usually manual reset) switch lockout.The limit switch is a component that activates and deactivates the unit’s blower assembly.The flame rollout switch is a safety device that will shut off the gas valve if it detects the presence of flame rollout.In a lot of cases, the unit will reset itself, once it cools down.You might have to reset the switch or replace the flame rollout protection device – the fuse link.
Code 1-4Ignition lockout means that your unit had detected an unsafe condition. In such a case, the controller shuts off fuel and power.Usually, the furnace will auto-reset in about 3 hours (it needs time to cool down). 
Code 2-1Gas heating lockout – the furnace shuts off fuel and power to prevent unsafe operation.Check the gas valve. If you don’t hear a clicking noise, once you turn the unit on, the valve might have to be replaced.There may be a problem with the control board. 
Code 2-2Abnormal flame-proving signal (the gas valve is de-energized, but the flame is proved).The gas valve might be leaky or stuck. You can use a clean cloth to wipe the valve and see if it helps.Warning! If there is a smell of gas, turn the furnace off, leave the house, and call a professional – there might be a leak
Code 2-3The pressure switch did not openFirst of all, turn off and unplug the furnace. Then, examine the system for any obstructions.The flue pipe might be obstructed or the pressure switch hose might be disconnected or damaged.
Code 2-4The secondary voltage fuse is open (the fuse is open and there is a shortage in low-voltage wiring)Check the secondary voltage wiring.Warning! If you don’t feel comfortable dealing with wires, call a professional.
Code 3-1One of the switches in the system didn’t close (draft safeguard, aux-limit switch, pressure, or blocked vent switch) Here, you would have to check a few things.Make sure that there is no blockage of vent/intake and that the drain is connected.The problem might be a defective pressure switch, blower motor, or capacitor.
Code 3-3Limit switch or flame roll-out switch is openClean the filter (or replace it with a new one) and make sure that the vents are not obstructed. In some cases, the blower wheel might be loose or you may have a defective blower. If your switch is open for 3 minutes or longer, the code will change to error code 1-3. Remember that the flame roll-out switch has to be reset manually, while the limit switch will reset automatically
Code 3-4Ignition proving failure – it looks like the control board didn’t sense a flame (or adequate flame) and decided to shut down. Clean the flame sensor with plain steel wool. Such a sensor is relatively cheap, so you can always buy a new one if the clean-up doesn’t help.Make sure that the switch on the gas valve is in the ‘on’ position.Use a manometer to ensure that there is proper gas pressure at the gas valve.The ground wire that is going to the gas manifold has to be secured. The flame sensor has to also be firmly attached to the surface.

How to Enter the Diagnostic Mode on a Carrier Infinity Thermostat?

Infinity thermostats are smart thermostats certified by ENERGY STAR that can be used with the heating and cooling units manufactured by Carrier.

Such devices have a lot of cool features. In this particular article, we are going to find out how to enter the diagnostic mode on your Infinity thermostat – a mode that puts every component of the system to test and then provides you with the repair codes, if necessary.

Carrier furnace error codes access on thermostat
  • The thermostat has a flip-down door on its bottom. Pull the door down.
  • Find the ‘setups’ area and press the ‘advanced’ button. Hold the button for around 10 seconds, until the ‘install/service’ menu appears on the screen.
  • The scroll button is located on the bottom of the device. Press it to get to ‘checkout’ on the menu (that’s how Carrier calls its diagnostic mode).
  • Wait for the system to check all of its components.
  • Soon, you’ll see a list of the components on the screen. ‘Yes’ means that everything is okay with the component.
  • Highlight ‘service info’ and select this option. If there is a problem with any component of the system, you will see the error code right next to it.

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

How Do You Clear the Error Code on a Carrier Infinity thermostat?

When a part of your system needs maintenance, a message will appear on your Infinity thermostat. 

Usually, the message will appear, if there is a problem with your air filter, UV lamps, or humidifier pads.

The alert might become annoying, especially, in case you have already fixed the problem. So, if you ever want to remove the message from the screen, follow these simple steps.

  1. To make the ‘accessory status’ menu appear on the LCD screen, hold the button located next to the right arrow (it might take a few seconds).
  2. Use the scroll button to go through the components.
  3. To reset the setting, simply press the button located next to the right arrow.
  4. Repeat the same steps for the other components, if there is such a need.
  5. To exit this menu, press the button located next to the left arrow. 

Related: Goodman, Lennox, Trane, Rheem, & Bryant Furnace Error Codes