What Is the Green Flashing Light on the Front of My Trane Furnace?

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Trane is well-known for its line of furnaces and air conditioners. Their high-efficient furnace, and own air flow system make the Trane brand desirable to many homeowners who are looking for a unit that will give them comfortable and inexpensive service. Like many furnaces, Trane provides a quick diagnostic check with a flashing light system which is either red or green depending upon the model.


A furnace has several different states that it can be in at any one time. It can be completely off, on but not being used, on and being used for heating, and not working for various reasons. It's difficult to tell the difference between some of these conditions, so Trane put an easy to understand code into a blinking green light on the front panel. Knowing the code tells what the Trane is doing at the time.


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Sequence Flashing

When the light is flashing in a sequence the Trane is communicating specific problems that need professional assistance. The light will flash for the sequence, then pause, and then flash again. By counting the flashes and matching it up with the chart on the back of the unit you can diagnose what is wrong before you call the heating service. The flashes range from two flashes to nine.


Two, Five or Six Flashes

Two flashes means that there is an external lockout because the unit has exceeded the number of tries to start. This is a safety feature that prevents the unit from continually attempting to start when there is a problem. Another important number is five flashes, which means there is a flame where there is not supposed to be one. Six flashes can sometimes be fixed by the homeowner by merely disconnecting the electrical plug from the wall outlet and putting it in upside down from the way it was before unplugging it. If this does not stop the blinking then you have a more major electrical problem that needs resolving.


Seven, Eight or Nine Flashes

Seven flashes indicate a problem with the gas valve, which should be checked immediately. Low flames are shown by eight flashes and nine flashes means the igniter must be checked. The igniter is only used when the furnace needs to start from a cold start so it is not as urgent as some of the others. However, if the furnace goes out and the igniter is not working, the furnace cannot turn back on without it being repaired.


Slow or Fast

If the green light is flashing slowly it means the furnace is on but there is no request for heat. When it is flashing fast the furnace is providing heat to the home. A continuous light means that the IFC circuit board needs replacing while a continuous off means the furnace is either off or not receiving any electrical power.



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