ServiceNomad RV · Knowledge
RV AC Freezing Up or Icing Over
Ice on your AC unit is never normal. If you see white frost on the coils, water dripping excessively, or airflow slowly dying over an hour, you have a freeze-up. This creates a snowball effect: ice blocks air, which makes it colder, creating more ice.
The Golden Rule: Airflow
Air conditioners balance pressure and temperature. For the coil to stay above freezing (usually 35-40°F), warm air MUST move across it. If you restrict airflow—dirty filters, closed ceiling vents, or crushed ductwork—the coil temperature drops below 32°F, and humidity turns to ice. Always keep at least 75% of your ceiling vents OPEN. Closing them all to force air into one bedroom increases backpressure and causes freezing.
Humidity Management
In humid climates (Florida, Texas), the AC is working double-time to remove moisture. If you run the fan on 'Low' or 'Auto', the air moves too slowly and gets too cold. Switch your fan to 'HIGH' (On/Manual). This high-speed constant airflow prevents frost from sticking to the fins.
The Freeze Sensor
Your unit has a specialized thermistor (temperature probe) stuck into the evaporator coil fins. Its job is to sense if the coil hits 33°F and shut off the compressor to let it thaw. If this probe falls out (common vibration issue) or fails, the AC will never know it's freezing and will run until it's a solid block of ice.
💡 Prevention Tips
- Run fan on HIGH in humid weather.
- Keep ceiling vents open.
- Check the divider gasket in the plenum for air leaks.
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