F- 0, 1 or 2 on screen
An F - message is a heat setting on your control unit.
Holding down the 'heat' and 'jets' buttons for 2-3 seconds at the same time and use the '+' or '-' to scroll through F - 0 to F - 2 to set maximum temperature.
F - 0 will allow 40º as the max temp
F - 1 will allow 38º as the max temp
F - 2 will allow 42º as the max temp