Overdefrosting is caused by:

• A. A defrost termination failure.
• B. Excess condensation during defrost.
• C. Low refrigerant charge.
• D. Excessive compressor run-time.

Answer: (A)

Defrost cycles melt frost and then stop at a specific point so the evaporator doesn’t stay warm longer than needed. The thing that controls stopping the defrost is the defrost termination mechanism—usually a thermostat or timer that signals when the ice is melted or the set time has elapsed. If that termination fails, the heater keeps running, leading to an overly long defrost period. That’s why overdefrost occurs: the defrost cycle doesn’t terminate when it should, so melting continues beyond what’s necessary.

Other factors like excess condensation during defrost, low refrigerant charge, or excessive compressor run-time don’t inherently cause the defrost cycle to keep going. They affect humidity, cooling performance, or efficiency, but they aren’t the failure mode that prolongs defrost.