Moffat Dryer Error Code F4

The F4 error code on a Moffat dryer indicates that the drying cycle has been interrupted before completing normally. This is a broad fault signal that tells the control board the drying process could not continue to its intended endpoint. Rather than pointing to a single failed component, F4 typically surfaces when the dryer detects an abnormal operating condition that forces it to halt the cycle as a protective or corrective response.

The most common systems involved in an F4 fault are the thermal protection circuit, the moisture sensing system, and the door latch assembly. If the dryer overheats due to restricted airflow or a failing heating element, thermal limiters or thermostats may cut power to the heating circuit, effectively interrupting the cycle. Similarly, if the moisture sensor bars become coated with residue, the control board may receive inaccurate readings and terminate the cycle early. A door switch that loses continuity mid-cycle can also trigger an interruption fault.

Diagnosing F4 requires a systematic check of airflow, door switch continuity, and thermal components. Begin by inspecting the exhaust vent path for blockages, as restricted airflow is a leading cause of thermally triggered cycle interruptions. Check the door switch for consistent continuity when the door is closed. If those check out, inspect the moisture sensor strips inside the drum for buildup and clean them with a mild abrasive. More advanced diagnosis may require checking thermistor resistance and thermal limiter continuity with a multimeter.