Trane Furnace Error Code 5

Error code 5 on a Trane furnace indicates either an open flame rollout switch or an open low voltage fuse on the control board. The flame rollout switch is a manual reset safety device that trips when flames extend outside the burner area. The low voltage fuse protects the 24-volt control circuit and can blow due to wiring shorts or failed accessories. Both conditions will prevent the furnace from operating until they are diagnosed and corrected.

Yes, this error code reflects a genuine safety event. A tripped rollout switch means flames left the combustion chamber, which can indicate venting problems, a cracked heat exchanger, or airflow issues that also raise carbon monoxide risk. The furnace should not be restarted repeatedly without a qualified technician inspecting the combustion system, venting, and heat exchanger.

No, resetting the furnace will not permanently clear error code 5 unless the underlying fault has been corrected. If the rollout switch was tripped, it must be manually reset at the switch itself, not just at the thermostat or power. If the root cause such as a flue blockage, heat exchanger problem, or wiring short is not addressed, the error will return and the safety device will trip again.

You can physically press the reset button on the flame rollout switch to restore continuity, but this should only be done after finding and fixing the root cause of the rollout condition. Resetting the switch without correcting the underlying problem is a fire and safety hazard, and the switch will trip again. If the issue is a blown fuse on the control board, that fuse must be replaced and the short circuit causing it must be located first.

Repair costs vary widely depending on the cause. Replacing a blown control board fuse is a low-cost fix, typically in the range of a standard service call fee. If the venting requires cleaning or correction, costs are moderate. A cracked or failed heat exchanger is the most expensive possibility, with replacement costs potentially ranging from several hundred to over a thousand dollars depending on the unit and parts involved.