Blinking Red Light On Furnace? (Possible Causes & Fixes)

Blinking Red Light on Furnace

Your house seems a little chilly, so you go out to your garage to check on the furnace. You notice it has a blinking red light- what does this imply?

A blinking red light on your furnace indicates a technical error specified by one of its many codes. Different problems range from faulty wiring and carbon build-up on furnace parts to reversed power polarity. The cost of remedying the issue could be anywhere from $150 to over $500.

In this article, we’ll talk about the most popular furnace brands and what their error codes mean. Look further down to find yours!

What Does a Blinking Red Light on a Furnace Mean?

Generally speaking, this means there is a problem either internally within the furnace system or with the thermostat it communicates with.

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Popular Furnace Brands and Blinking Red Lights

Each furnace exhibits error codes unique to the machine itself. Decoding what your furnace is trying to tell you is essential to finding the right fix.

Here are the 3 most used furnace brands that we’ll be discussing in detail:

  • Lennox furnace
  • Luxaire furnace
  • York furnace

Take a look at the specifics below!

Lennox Furnace Error Codes: Blinking Red Light

On a Lennox furnace, there are two LED lights that flash or signal independently. The most common blink codes are:

LED light #1: Slow Blinking | LED light #2: Slow Blinking

  • Your Lennox furnace is functioning completely normally.

LED light #1: Fast Blinking | LED light #2: Fast Blinking

  • Your furnace is functioning normally, and there is a call for heat from your thermostat.

LED light #1: Slow Blinking | LED light #2: Solid

  • This code means that the limit switch is open. The limit switch is responsible for turning on the furnace blower when the desired temperature (according to the thermostat) is reached.
  • A scenario like this means that the furnace has overheated and is most commonly the result of a dirty filter or blower wheel.
  • To fix this, you must replace your air filter, clean the blower wheel, and allow for the furnace to cool down. If you suspect that your limit switch is broken, it’s essential to replace it ASAP.

LED light #1: Off | LED light #2: Slow Blinking

  • If the first LED light is ‘Off,’ and the second is exhibiting a slow flash, there’s a problem with the pressure switch that usually can’t be repaired.
  • To fix this, first, check your filters to make sure they’re clean. If so, replace the pressure switch. Expect to pay around $150.

LED light #1: Alternating Slow Blinking | LED light #2: Alternating Slow Blinking

  • This indicates a failure involving the flame. The pilot light or ignition sensor is most likely to blame. You might hear your furnace click on; however, it will never start up fully.
  • To fix this, turn off your furnace and clean both the pilot light and ignition sensor. If that doesn’t work, one or both of these parts will need to be replaced.

LED light #1: Alternating Fast Blinking | LED light #2: Alternating Fast Blinking

  • When both lights are blinking fast, either the ignitor is broken, or the system has low voltage.
  • To fix this, check your outlets (make sure they’re working properly). If so, replace the ignitor.

LED light #1: Slow Blinking | LED light #2: Off

  • A code like this means that there is a flame detected without the gas valve turned on. This is a classic leaky gas valve issue.
  • To fix this, allow for your machine to cool off (gas can get dangerous, especially when the furnace is hot) and inspect for a leak.
  • If you see one, call in a technician to do a repair. This isn’t something you want to attempt yourself.

LED light #1: Solid | LED light #2: Slow Blinking

  • When you see this pattern, understand that it points to an open flame rollout switch. A broken inducer or burner could be the source of this.
  • To fix this, find the reset button on the side of your machine. Hold this down for a few seconds to reset the system!

LED light #1: Blink, Blink, Off | LED light #2: Blink, Off, Blink

  • This unique code is indicative of a problem with your furnace’s wiring or an IFC (the mastermind of the furnace) failure. It’s unknown what may cause this.
  • To fix this, call your local HVAC technician. Usually, this is a complex issue involving re-wiring and troubleshooting the electrical components of your Lennox furnace.

LED light #1: Fast Blinking | LED light #2: Slow Blinking

  • If the first light is blinking fast, and the second is blinking slow, the power polarity is reversed in your outlet.
  • What this means is that a neutral wire is connected to where a hot wire is supposed to be inside your outlet. The problem with this is that your furnace will always be receiving electricity, even when it is turned off. This is a major fire hazard.
  • To fix this, contact a qualified technician. The Youtube videos seem temptingly easy, but this issue can get complicated quickly.

LED light #1: Slow Blinking | LED light #2: Fast Blinking

  • This points to a low flame signal. Typically, this is caused by carbon build-up on the sensor and not a broken sensor itself (although it’s possible).
  • When this happens, your furnace will not be able to generate enough heat or may trick itself into overcompensating and supplying too much heat.
  • Regardless, to fix this, clean off the flame sensor!

York and Luxaire Furnace Error Codes: Blinking Red Light

Here are the blinking red light error codes of a York and Luxaire furnace and what each one means. Most of their codes overlap, with a few exceptions.

1 Blinking Red Light

  • This indicates no power is provided to the gas valve, and a flame is still present. The most common cause for this is a leaky gas valve.
  • To fix this, allow for the furnace to cool down. The machine has a fan intended to lower the temperature when overheating occurs. Check the gas valves for any leaks and use caution as things can get hot and dangerous.
  • You may need to call a technician to repair the gas valve so as not to leave an ongoing fire hazard unattended. It could be as easy as applying some Teflon tape.

2 Blinking Red Lights

  • The pressure switch is stuck in the closed position when this code appears on your York furnace. Possible reasons for this include damaged pressure switch wires or rusty parts.
  • To fix this, see if your pressure switch has visible signs of wear. If so, replace it immediately. Using a professional, the average cost to replace this part is around $150- much cheaper than buying an entirely new furnace!

3 Blinking Red Lights

  • This happens when the pressure switch is stuck in the open position. The most common reason this happens is due to warped parts if your furnace hasn’t been used in some time.
  • It could also be the result of incorrect pressure reading. If the inducer is on, the pressure switch should be activated.
  • To fix this, troubleshoot the inducer and ensure the boiler pressure is between 1.5 and 2 bar. If these parts are fully functioning, your pressure switch will need to be replaced.

4 Blinking Red Lights

  • Should this blink-code occur, take a look at the high-limit switch (similar to a pressure relief valve on an air compressor). In this case, it’s usually open.
  • This is often the result of a blown fuse, a malfunctioning pressure switch, or a dirty air filter.
  • To fix this, replace your air filter. As a general rule of thumb, this should be done once every 3 months to keep your furnace in good working order. Check out the fuses and troubleshoot the furnace’s pressure switch to ensure neither of these is to blame!

5 Blinking Red Lights

  • Five blinking red lights usually signal that a rollout switch or an auxiliary limit switch is open. A faulty inducer or an issue with the burner can cause this.
  • To fix this, look for a red rollout reset button on the side of your York furnace. Pressing this will reset the entire system!

6 Blinking Red Lights

  • If your York furnace blinks red 6 times, the modulating gas valve is experiencing a failure. This can be damaging to the entire system because this part allows propane or natural gas to flow into your unit.
  • The only way to fix this is by replacing the modulating gas valve. This can be pricey and costs around $400 for the parts and labor.

7 Blinking Red Lights

  • This indicates your furnace is in “lockout mode.” It tried to ignite a flame three times and, unfortunately, was unsuccessful. At this point, the furnace will be locked down for 60 minutes.
  • Once that time is up, it will attempt to start a flame again. This process will repeat until a flame is sensed.
  • To fix this, wait an hour until the lockout mode ends. If your York furnace is stuck in this perpetual cycle, call a technician to override this mechanism and fix the problem.

8 Blinking Red Lights

  • The flame is lost 5 times during the heating cycle of your York furnace when the eight-red-light blink code is displayed.
  • Insufficient gas pressure, dirty flame sensors, or a broken gas valve can all contribute to this. The furnace will once again enter “lockout mode” for 60 minutes.
  • To fix this, wait for the lockout mode to end. Call a technician if the problem persists.

9 Blinking Red Lights

  • Nine red blinking lights on your York furnace let you know the machine is experiencing a grounding issue.
  • To fix this, call in a technician to properly handle the problem. Oftentimes, the causes are unknown and could require an entirely new furnace.

10 Blinking Red Lights (*Only Applicable to Luxaire)

  • This means the gas valve is stimulated with no heat, usually caused by a gas valve wiring issue.
  • To fix this, check the wires on your machine and reach out to a technician if you can’t troubleshoot the issue on your own.

11 Blinking Red Lights (*Only Applicable to Luxaire)

  • The primary or auxiliary limit switch is stuck open (and has been for 5 minutes or longer) when you see 11 red light flashes. Common causes are a bad blower motor or faulty blower wheel.
  • To fix this, press the reset button on the side of the furnace.

Solid Red Light

  • When your York furnace exhibits a solid red light, the control board has blown.
  • To fix this, you must replace the entire control board. This will set you back around $500.

Continuous Blinking Red Lights

  • When constant blinking happens, there is a twinning error, and you have an issue with your thermostat wiring.
  • To fix this, turn off your furnace and connect the leads on the R and W terminals of your thermostat. After that, power the furnace back on.

Related Questions

My furnace isn’t blowing air. What does this mean?

If your furnace isn’t blowing air, your filter is probably clogged. Swap it out for a clean one to solve the problem and prevent overheating!

How much does it cost to get your furnace flame sensor replaced?

Depending on who you call and where you live, it costs around $425 to get a new flame sensor installed.

Why does my furnace smell weird?

When you go to turn on your heat for the very first cool fall day, you smell a musty, funky smell. What could that be?

If your furnace is left untouched for a while, dirt, debris, and moisture collect in your air ducts. Once you turn your furnace on, all of this material burns and smells a little. Usually, this fades over time and isn’t something to worry about!

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Wrapping It Up

If your furnace is blinking a red light, try some of the tips and tricks above to fix it!

If any issue seems like too large of an undertaking, call an HVAC technician to help. You never want to put yourself at risk for burning or electrocution.

Emily Carr

Emily is a copywriter with over five years of experience in crafting content for the home renovation and remodeling industry. She loves house projects, whether it be painting a room or tweaking small design elements to transform a space. Her favorite aesthetic is french modern because of its clean lines and airy feeling! When not writing, Emily loves to travel and check out architectural details all over the world.

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