What would likely cause a time-initiated temperature-terminated defrost to run full time during light coil frosting?

The scenario described involves a time-initiated, temperature-terminated defrost cycle running continuously during light coil frosting. This condition is predominantly influenced by the behavior of the defrost thermostat.

A faulty defrost thermostat would fail to accurately sense the temperature at the evaporator coils. If the thermostat is malfunctioning, it may not detect that the coils are sufficiently warm or that the frost has been removed. As a result, the system could keep the defrost cycle active for an extended period, leading to a full-time operation of the defrost function even in the presence of only light frosting.

In a properly functioning system, the defrost thermostat is responsible for terminating the defrost cycle once the temperature reaches a certain threshold, allowing the evaporator coils to return to normal operation. When this device is impaired, it cannot perform its role effectively, causing the system to misinterpret the need for defrost and unnecessarily prolong the cycle.

This understanding helps distinguish how critical the defrost thermostat is in regulating the defrost cycle against other components. For instance, a faulty compressor can impact total system performance, but it wouldn’t necessarily lead to continuous defrosting in this specific context. Similarly, low refrigerant levels or dirty evaporator coils would affect system