Goodman HVAC Error Code 5

Fault code 5 on a Goodman furnace means the ignition control is detecting a flame signal when no flame should be present, a condition called false flame sensing. This causes the control to lock out operation as a safety measure. The most common sources are a sticking gas valve that won't fully close or a problem in the flame sense circuit, such as a grounded sensor rod or damaged wiring.

The fault code itself represents the furnace's safety system working correctly by shutting down when an unexpected flame condition is detected. A sticking gas valve, if confirmed, is a serious concern because uncontrolled gas flow creates combustion and carbon monoxide risks. The system should not be bypassed or repeatedly reset without identifying and correcting the underlying cause.

Resetting the furnace by cycling power may temporarily clear the fault and allow the unit to attempt operation again, but it will not resolve the underlying problem. If the sticking valve or flame sense circuit issue remains, the fault will return, often quickly. Repeated resets without repair can mask a developing problem and should be avoided until a proper diagnosis is completed.

Some steps, like inspecting and cleaning the flame sensor rod, are within reach of a confident DIYer. However, diagnosing a sticking gas valve or tracing a wiring fault in the flame sense circuit typically requires technical experience and appropriate tools. Replacing a gas valve involves working with the gas supply line, which should be performed by a licensed technician in most jurisdictions.

Repair costs depend on the root cause. Cleaning the flame sensor is a low-cost service call repair, generally in the range of $75 to $150 including labor. Replacing a flame sensor rod typically adds a modest parts cost on top of labor. A gas valve replacement is more involved, with parts and labor commonly ranging from $300 to $600 or more depending on the model and local labor rates.