HVAC Error Code E2 — What It Means & How to Fix It

What Does This Error Mean?

E2 means the coil temperature sensor (also called the evaporator or pipe sensor) has a problem. This sensor monitors the temperature of the cooling coil inside your unit. It prevents the coil from freezing over by telling the system when to cycle off. When this sensor fails, the unit may freeze up, short cycle, or stop cooling. Replacing the sensor usually fixes the problem quickly.

Affected Models

Mini-split air conditioners
Window AC units
Portable air conditioners
Heat pumps
Central air handlers

Common Causes

Coil temperature sensor has failed or drifted out of its normal range
Sensor wire is pinched, disconnected, or damaged inside the unit
Ice buildup on the evaporator coil has damaged or displaced the sensor
Corroded sensor connector on the main control board
Sensor is not making proper contact with the evaporator coil surface

How to Fix It

Turn off the unit and unplug it. If the coil is frozen, let the unit thaw completely before working on it. This may take several hours with the unit off and the fan running.

Never try to chip or scrape ice off the coil. You can puncture the refrigerant tubing and cause a much bigger problem.
Open the front panel or access cover to reach the evaporator coil. The coil sensor is usually a small probe clipped or taped directly to the coil tubing.

On mini-splits, remove the front panel filters first. The sensor is often on the coil behind the filters.
Check that the sensor is firmly attached to the coil and that its wire is securely plugged into the control board. Reattach it if it has fallen off or come loose.

The sensor must be in good contact with the coil to read temperature accurately. A loose sensor gives wrong readings.
Replace the coil temperature sensor if it appears damaged or if reattaching it doesn't fix the error. Order the exact part for your make and model.

Coil sensors cost $5-$25 for most brands. Installation takes just a few minutes with no special tools.
Reassemble the unit, plug it back in, and turn it on. Run it in cooling mode and verify the E2 code is gone. Monitor for any ice forming on the coil over the next hour.

If the coil still freezes even with a new sensor, the problem may be low refrigerant or a dirty air filter restricting airflow.

When to Call a Professional

If the sensor and connections look fine but E2 persists, call an HVAC technician. A frozen coil can be caused by low refrigerant, which needs professional service. The control board may be faulty and require replacement. A technician can measure the sensor's resistance to confirm if it's good or bad. Expect $100-$250 for a service call and diagnosis.

Frequently Asked Questions

Why does my AC coil freeze up?

Several things can cause a frozen coil. A clogged air filter restricts airflow over the coil. Low refrigerant levels drop the coil temperature too low. A faulty coil sensor can't tell the system to stop before freezing. Running the AC when it's too cold outside can also cause freezing. Start by checking your air filter and making sure vents aren't blocked.

Is E2 the same as E1?

No, they're different sensors. E1 is the room temperature sensor that measures ambient room air. E2 is the coil temperature sensor that monitors the evaporator coil. E1 affects temperature regulation and cycling. E2 affects freeze protection and defrost operations. Both are small thermistor sensors but they do different jobs.

Can a dirty filter cause E2?

Not directly, but indirectly yes. A dirty filter reduces airflow over the evaporator coil. Reduced airflow lets the coil get too cold and freeze. Ice on the coil can damage or displace the temperature sensor. Always keep your air filter clean to prevent coil-related problems. Check and clean your filter at least once a month during heavy use.