If a restriction clears up when the system is turned off and allowed to warm, the restriction was probably due to:

• A. Moisture
• B. Loose Fittings
• C. Overcharge
• D. Contaminated Refrigerant

Answer: (A)

Moisture in the system can freeze in the metering device (such as a capillary tube or expansion valve) when the refrigerant is cold. That ice acts as a plug, creating a restriction. When you turn the system off and it warms up, the ice melts and the flow is restored, so the restriction disappears. This temperature-dependent effect is why moisture is the best explanation. Loose fittings would mainly cause leaks, not a temporary blockage that clears with warming. An overcharge tends to cause pressure and flow issues that don’t simply vanish with heat. Contaminated refrigerant can cause blockages too, but they don’t typically clear just by warming the system. Ensuring proper vacuum evacuation and drying the system helps prevent moisture-related restrictions.