What does Fujitsu Mini Split Ice on Coils - Causes & Fix mean?

Ice on indoor coils is usually caused by a dirty air filter or clogged evaporator blocking airflow. Clean or replace the filter first.

How do I fix Fujitsu Mini Split Ice on Coils - Causes & Fix?

Follow the step-by-step diagnosis below. The most likely fix is identified by checking power, sensor resistance, and control-board signals in order — using a multimeter and the part numbers documented in the parts reference table.

Can I keep running the equipment with this fault active?

Generally no. Faults on Hvac units are emitted when a sensor, safety, or control circuit is outside its operating envelope. Running through an active fault risks compressor, heater, or control-board damage. Diagnose and clear the fault first.

What part is most commonly replaced for Fujitsu Mini Split Ice on Coils - Causes & Fix?

The most frequently replaced parts for Fujitsu Mini Split Ice on Coils - Causes & Fix are listed in the Parts Reference section of this guide with OEM part numbers and typical price ranges. Check the table for direct replacements.

Is Fujitsu Mini Split Ice on Coils - Causes & Fix a DIY repair or do I need a technician?

Sensor swaps, fan motor replacements, and condenser cleaning are typical DIY-level repairs. Anything involving refrigerant, gas, or high-voltage (>240V) work requires a licensed technician for both safety and code-compliance reasons.

Fujitsu Mini Split Ice on Coils - Causes & Fix

Fujitsu Mini Split Ice on Coils — What’s Happening

Ice forming on your Fujitsu mini split’s indoor evaporator coil means the coil surface temperature has dropped below freezing, causing moisture in the air to freeze on contact. This happens when something prevents the coil from absorbing enough heat from the room air, or when the refrigerant side is operating incorrectly. If you see an error code displayed along with the ice, E5 is the most common Fujitsu code related to icing. E5 indicates the indoor coil thermistor (temperature sensor) has a short circuit, which means the indoor unit cannot read the evaporator temperature correctly and may not regulate defrost or refrigerant flow properly.

Jump to Fix

Most Likely Causes

Dirty or clogged air filter A restricted filter blocks airflow across the evaporator coil, dropping coil temperature low enough to freeze moisture on the fins.
Dirty evaporator coil or blower wheel Dust and debris buildup on the coil itself or on the blower wheel reduces airflow and causes the same freezing effect as a clogged filter.
Blower motor or fan failure If the indoor fan runs weakly or not at all, airflow drops and the coil temperature falls below freezing.
Low refrigerant charge or refrigerant leak Insufficient refrigerant causes the evaporator to run too cold, creating frost and ice on the coil and copper lines.
Faulty indoor coil thermistor A shorted or open thermistor (temperature sensor) prevents the system from reading coil temperature correctly, which can disable defrost protection and allow icing.
Bad thermistor wiring or connector Damaged wiring, loose connections, or moisture in the sensor connector can create false temperature readings or trigger an E5 code.
Failed indoor control board If the thermistor tests good but the system still misreads temperature or reports E5, the indoor PCB sensor circuit may be faulty.

How to Diagnose and Fix

Inspect the indoor evaporator coil and copper lines for visible frost or ice buildup.
Check the air filter and replace or clean it if dirty or clogged.
Turn the unit off and allow the coil to defrost completely before further testing.
Remove the front cover and inspect the blower wheel and evaporator coil for dust or debris, and clean if needed.
Verify the indoor fan runs at full speed and delivers strong airflow from the supply vents.
With power off, disconnect the indoor coil thermistor connector and measure the sensor resistance with a multimeter, then compare the reading to the manufacturer’s temperature-resistance chart.
Inspect the thermistor harness and connector for damage, corrosion, loose pins, or moisture intrusion.
If airflow and sensors test good, call a technician to check for refrigerant leaks, verify system charge, and perform refrigerant-side diagnostics including pressure and superheat measurements.

Parts You Might Need

Part	Notes
Indoor coil thermistor	Amazon \| Temperature sensor on the evaporator coil, often triggers E5 code when shorted or open.
Indoor control board / PCB	Amazon \| Main board for the indoor unit, replace if sensor circuit misreads a good thermistor.
Indoor blower motor	Amazon \| Fan motor for the air handler, replace if weak or non-functional.
Air filter	Amazon \| Standard washable or replaceable filter, clean or replace as part of routine maintenance.

If your appliance also shows a code on the display, these match this problem:

When to Call a Pro

Call a professional if the coil continues to ice up after you have cleaned the filter, blower wheel, and evaporator coil and confirmed strong airflow. Refrigerant leaks, charge verification, thermistor testing against factory specs, and indoor board diagnostics require gauges, leak detectors, and model-specific service data. If you see an E5 code or other fault code along with the ice, a technician can test the sensor circuit and replace the thermistor, harness, or control board as needed. Any work involving refrigerant recovery, evacuation, or recharge must be done by an EPA-certified technician.