⚠
warning Honeywell
Error Code 187
Clean or replace ventilator filter — the ventilator filter needs maintenance.
? What Causes This
Ventilator filter has accumulated dust or reached its service life.
✓ How to Fix It
Clean or replace the ventilator filter or contact your heating or cooling professional. Reset the timer by touching Dismiss on the thermostat screen after completion.
Source: page 28 of the official manual
From the manual
