What this code means
The manual identifies F1 as an open- or short-circuited indoor ambient temperature sensor.
Safe checks
- Confirm the thermostat is on, set correctly, and calling for heating or cooling.
- Check the air filter and visible return-air path for obvious airflow restrictions.
- Record the displayed code or flash sequence before scheduling service.
First step
Record the code, check the thermostat and filter, and schedule service if the condition remains.
Frequently asked questions
What does F1 mean on a TOSOT TM48D6MO?
The manual identifies F1 as an open- or short-circuited indoor ambient temperature sensor.
What should I safely check before scheduling service?
Use only the visible, non-invasive checks listed on this page. Do not open equipment panels.
When should GreenFlow handle this code?
Call GreenFlow if the code repeats, the equipment is locked out, heating or cooling is not restored, or the condition involves gas, ignition, pressure, wiring, a motor, or a control board.