⚠
warning Honeywell
Error Code 181
Replace air filter (1) — the air filter needs to be replaced.
? What Causes This
Air filter has reached its service life.
✓ How to Fix It
Replace the air filter or contact your heating or cooling professional. Reset the air filter timer by touching Dismiss on the thermostat screen after replacement.
Source: page 27 of the official manual
From the manual
