A crankcase _______ is often used to prevent refrigerant from migrating to the oil during periods of low ambient temperature.

• A. Valve
• B. Insulation
• C. Pump
• D. Heater

Answer: (D)

When temperatures are low, refrigerant tends to migrate into the compressor crankcase and can condense in the oil, diluting lubrication and causing startup problems. A crankcase heater is an electric heating element placed in the crankcase to keep it warm, which prevents refrigerant from condensing in the oil and helps vaporize any refrigerant that has migrated. This keeps the oil properly lubricated and reduces the risk of compressor damage on startup. The other options don’t actively stop refrigerant migration—valves control flow, insulation slows heat loss but doesn’t prevent condensation, and a pump moves refrigerant rather than addressing condensation in the oil.