RV AC Freezing Up? Fix Ice on Coils in 5 Steps

Tools & Parts Needed

Find these on Amazon: RV Air Filter Replacement , Fin Comb Tool , Digital Multimeter

The Problem

When your RV air conditioner freezes up with ice on the coils, it's typically caused by restricted airflow from a dirty filter, blocked vents, or low refrigerant levels. Turn off the AC immediately and let the ice melt completely before attempting any repairs to prevent damage to the compressor.

Root Causes

Dirty Air Filter: The most common cause is a clogged filter restricting airflow over the evaporator coils. Dometic and Coleman RV AC units are particularly sensitive to dirty filters.

Blocked Vents: Furniture or curtains blocking return air vents reduces airflow, causing coil temperatures to drop below freezing.

Low Refrigerant: Refrigerant leaks cause the evaporator coils to get too cold. This requires professional repair as it involves sealed refrigeration systems.

Thermostat Issues: A malfunctioning thermostat may not cycle the compressor properly, leading to overcooling.

Dirty Evaporator Coils: Dust and debris on coils restrict heat transfer, similar to a dirty filter effect.

Fan Motor Problems: A failing blower motor reduces airflow over the coils, causing freeze-up.

The Solution

You'll need:

• Replacement air filter (if needed)
• Vacuum cleaner with brush attachment
• Soft brush or fin comb
• Multimeter
• Flashlight or headlamp
• Basic hand tools

Follow these steps:

1. Turn off the AC immediately - Switch off power at both the thermostat and breaker to prevent compressor damage
2. Let ice melt completely - Wait 2-4 hours for all ice to thaw naturally
3. Remove and inspect the air filter - Located in the return air grille, remove the filter and check for dirt buildup. Replace if heavily soiled or clean if washable
4. Check all air vents - Ensure no furniture, curtains, or debris are blocking supply or return vents inside the RV
5. Inspect the evaporator coils - Look for dirt buildup on the coils. Clean gently with a soft brush if dirty
6. Check the condensate drain - Ensure the drain pan and drain line aren't clogged, causing water backup
7. Test the thermostat - Verify the thermostat is reading temperature correctly and not set too low (below 68°F)
8. Restart and monitor - Turn the AC back on and monitor for 30 minutes to ensure normal operation

Red Flags That Need a Pro

Contact an RV technician if you experience: repeated freeze-ups after cleaning filters and clearing blockages, refrigerant leaks (oily residue around fittings), compressor not starting, or electrical issues with the control board. Refrigerant work requires EPA certification and specialized tools.

Keeping This From Happening Again

Replace or clean air filters monthly during heavy use periods. Keep return vents clear of obstructions and maintain at least 6 inches of clearance around all vents. Set thermostat no lower than 68°F, especially in humid conditions. Schedule annual professional maintenance for Dometic, Coleman, or Suburban AC units to check refrigerant levels and clean coils thoroughly.

Consider upgrading to a programmable thermostat that prevents overcooling, and always ensure adequate power supply (typically 12-16 amps depending on unit size) as low voltage can cause compressor issues leading to freeze-up.