Trane Furnace Error Code 6 Flash

A 6 Flash code means the furnace control board has detected one of five electrical faults: reversed line polarity, a missing earth ground, an open or shorted igniter circuit, a triac voltage error, or AC supply voltage that is too high. The board stores the specific fault type in its fault history log, accessible through the user interface. Because the code covers multiple possible causes, reviewing the last four stored faults is the essential starting point for diagnosis.

Yes, some of the underlying causes are genuine safety concerns. Reversed line polarity and a missing earth ground are electrical hazards that should not be ignored or bypassed. The furnace correctly refuses to operate under these conditions to protect both the equipment and the occupants. Do not attempt to override the lockout without first correcting the root cause.

Repair costs vary depending on the cause. Correcting a wiring polarity or grounding issue typically involves labor only, ranging from roughly 80 to 200 dollars. A hot surface igniter replacement, including the part and labor, generally runs between 150 and 350 dollars. If the control board itself has a failed triac and requires replacement, costs can range from 350 to 700 dollars or more depending on the board and labor rates in your area.

Some causes are within reach of a confident DIYer. If the fault history points to a polarity or grounding error, checking and correcting the wiring at the supply disconnect may resolve it. Replacing a failed hot surface igniter is also a common DIY repair once the igniter resistance confirms it is out of the 11 to 18 ohm range. However, diagnosing a faulty control board triac or measuring and correcting high line voltage should be handled by a licensed technician.

Resetting the furnace by cycling power may temporarily clear the fault display, but the code will return quickly if the underlying problem has not been corrected. The control board stores the fault in its history log, so even if the display resets, the fault record remains. Resetting without diagnosis is not a repair and can delay finding a potentially serious electrical fault.