Trane Furnace Error Code 6 RED

The 6 RED flash code on a Trane furnace means the 1st stage pressure switch opened five times within one heating cycle, causing a one-hour safety lockout. The pressure switch monitors whether the inducer motor is creating enough draft for safe combustion. When it fails to stay closed repeatedly, the control board shuts down the furnace to prevent unsafe operation. The furnace will attempt to restart automatically after the one-hour lockout period ends.

The furnace is designed to stop firing when this error occurs, so it is not actively burning fuel during the lockout period. The lockout itself is a safety feature preventing potentially unsafe operation due to inadequate draft. It is not safe to bypass or defeat the pressure switch, as proper draft is essential for venting combustion gases out of the home. Address the root cause before restoring normal operation.

The most common causes are a blocked or restricted flue vent and a cracked or clogged pressure switch hose. Both conditions prevent the pressure switch from detecting adequate draft, causing it to open repeatedly during the heating cycle. Checking the exterior vent termination for obstructions and inspecting the pressure switch hose for damage or moisture are good first steps before moving on to more involved diagnostics.

The furnace will reset itself automatically after the one-hour lockout period without any intervention. You can also manually reset the furnace by turning the power off and back on, which clears the lockout immediately. However, if the underlying cause of the pressure switch fault is not corrected, the 6 RED code will return and the lockout will occur again.

Repair costs vary widely depending on the cause. If the issue is a blocked vent or a simple hose replacement, costs may range from around $75 to $200 including a service call. An inducer motor replacement is more involved and typically falls in the range of $350 to $700 or more depending on parts and labor rates in your area. A pressure switch replacement alone generally ranges from $100 to $250.