Error 21 — Indoor coil frosted

What does 21 mean?

The indoor coil has frosted over. This is often caused by insufficient heat, low operating temperatures, or restricted airflow.

• Lack of heat in the conditioned space
• Operating indoor unit at excessively cold air temperature
• Blockage of airflow to the indoor unit
• Issue with the indoor fan motor

Click steps to track your progress.

1. 1

   Ensure the conditioned space is at an appropriate temperature.

2. 2

   Check and clean air filters.

3. 3

   Verify that air vents are not blocked.

4. 4

   Inspect the indoor fan motor operation.

5. 5

   Allow the system to enter its anti-freezing cycle.