Overload Protector
Function
The overload protector serves as a critical safety device that protects the compressor motor from damage due to excessive current draw, overheating, or abnormal operating conditions. This small but essential component monitors the electrical current flowing to the compressor and automatically interrupts power when conditions exceed safe operating parameters. The protector essentially acts as an automatic circuit breaker specifically designed for compressor motor protection, preventing costly motor damage and potential fire hazards that could result from uncontrolled overcurrent conditions.
Most refrigerator overload protectors use a bi-metallic disc or strip that responds to both current and temperature. Under normal operating conditions, the bi-metallic element remains in a closed position, allowing current to flow freely to the compressor motor. When excessive current flows through the protector, the bi-metallic element heats up due to increased electrical resistance. Additionally, if the compressor motor itself overheats, the protector mounted directly on the compressor housing will also heat up. When the temperature exceeds the protector's trip point, typically between 200°F and 300°F (93°C to 149°C), the bi-metallic element flexes and opens the electrical contacts, immediately stopping current flow to the compressor.
After tripping, the overload protector automatically resets as it cools down, typically requiring 5 to 15 minutes depending on the specific design and ambient temperature. This automatic reset feature allows the compressor to restart once normal conditions return, eliminating the need for manual intervention in most cases. However, if the underlying problem causing the overload condition persists, the protector will continue to trip repeatedly until the root cause is addressed.
Symptoms of a Broken Overload Protector
A malfunctioning overload protector typically causes compressor starting and running problems that can be challenging to distinguish from other electrical component failures. The most common symptom is intermittent compressor operation, where the unit starts normally but shuts down after brief periods, often accompanied by clicking sounds as the protector trips and resets. This cycling pattern may repeat every few minutes as the protector cools down and attempts to restart the compressor.
If the overload protector fails in the open position, the compressor will not start at all despite having proper electrical power and functional start relay components. The refrigerator may appear completely dead from a cooling standpoint, while other electrical components like lights and controls continue to function normally. This condition often confuses users who assume a major compressor failure has occurred when the actual problem is a relatively inexpensive overload protector.
Conversely, an overload protector that fails in the closed position poses serious safety risks since it cannot protect the compressor from overcurrent conditions. While this failure mode is less common, it can lead to compressor motor damage, electrical fires, or other dangerous conditions if the compressor experiences genuine overload situations. Symptoms might include continuous compressor operation even under abnormal conditions, unusual motor heating, or eventual compressor motor failure.
Repair Solutions
Diagnosing overload protector problems requires systematic testing to eliminate other potential causes of compressor malfunction. Begin by unplugging the refrigerator and allowing the compressor to cool completely, as a hot compressor can cause normal overload protectors to remain open. Wait at least 30 minutes before beginning diagnosis to ensure accurate testing results.
Locate the overload protector, typically mounted directly on the compressor housing near the start relay and electrical terminals. The protector is usually a small round or rectangular component with two or three wire terminals. Remove the protector by unplugging it from the compressor terminals or disconnecting the wire harness, depending on the specific mounting design.
Test the overload protector using a multimeter set to continuity mode. At room temperature, a functional protector should show continuity between its input and output terminals. If no continuity exists after the protector has cooled completely, the unit has likely failed in the open position. Testing the trip function requires specialized equipment and is typically not practical for field diagnosis, so temperature and continuity testing are the primary diagnostic methods.
Visual inspection can sometimes reveal protector problems, particularly signs of overheating such as discolored housing, melted terminals, or burn marks around the mounting area. However, many protector failures are internal and show no external symptoms, making electrical testing essential for accurate diagnosis.
When replacement becomes necessary, obtain an exact replacement protector using the part number from the original component or the refrigerator's service manual. Overload protectors are specifically matched to compressor motor characteristics, and using incorrect specifications can result in nuisance tripping or inadequate protection. Install the new protector in the same orientation and location as the original, ensuring all electrical connections are clean and tight. After installation, test the compressor operation through several start-stop cycles to verify proper protector function and confirm that the cooling system operates without premature shutdowns.