What Does a Furnace Light Blinking Green Mean?

When the furnace light blinks green, it usually means it has finished its diagnostic self-check. If your furnace has a green light that flashes, it is working fine, and you don’t need to worry. If the green light stays on or flashes on and off, it could signify a problem. These furnace error codes can help you uncover specific issues.

How do you read a furnace error code?

Every furnace comes with a manual that lists the manufacturer’s different codes. These codes are also often attached to the circuit board on the back of the furnace. While furnaces have different patterns, the way a code is read and the errors reported are often very similar. Let’s look at some of the most common furnace error codes and what they mean.

Sequence flashing

When the furnace’s green light flashes in a pattern, the unit tells you about specific problems that need help from a professional. During the sequence, the light will flash, stop, and then flash again. Before you call a heating service, you can figure out what is wrong by counting the flashes and comparing them to the chart on the back of the unit. There are anywhere from two to nine flashes.

Number of flashes

Two green flashes mean the unit is locked out from the outside because it has tried to start too many times. This safety feature stops the unit from trying to start repeatedly when something is wrong.

Five flashes is another important number. It means that there is a flame where there shouldn’t be one.

Six flashes indicate an issue with line voltage polarity or wiring, etc. You can sometimes fix this by resetting the circuit breaker. If this doesn’t stop the lights from blinking, you have a bigger electrical problem that needs to be fixed.

If the furnace flashes seven times, the gas valve must be checked immediately.

Eight flashes mean the flame is low, and nine flashes mean the igniter needs to be checked. The igniter is only used when the furnace needs to be started from cold, so it is less important than others. But if the furnace goes out and the igniter doesn’t work, it won’t start up again until it’s fixed.

Slow or Fast flashes

If the green light flashes slowly, it means the furnace is on, but there is no request for heat.

When it flashes quickly, the furnace heats the house. If the light stays on all the time, the circuit board must be replaced. If the light stays off all the time, the furnace is either off or not getting any electricity.

Yellow flash

If your furnace has a yellow light, turn it off and call a technician. If your furnace has a yellow light, it means that dirt is stopping oxygen from getting in. If the light goes out, that’s another sign of something wrong with your furnace.

It would be best if you looked at your manuals to figure out what the furnace light blinking green is. You can also call a qualified HVAC technician to do a full diagnostic on your furnace. We warn you to avoid removing the furnace error codes by resetting the circuit breaker to stop the green lights from blinking.

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About Mas Broto

Have been in the heating and air conditioning (HVAC) industry for over 20 years. He is person that will grow and thrive to learn more about the HVAC industry throughout his career. Mas Broto is also a blogger, who's dedicated to bringing you the best knowledge to get ahead in the game of life.