Turn the knurled ring to 
.
The warning light 
on the instrument
cluster will come on.
See also:
Diesel fuel filter sensor failure
The warning light on the dial comes on (on certain versions together with the
message on the display) when dieel fuel filter sensor failure is detected. Contact
Fiat Dealership as soon as poss ...
Capacities
(❒) For use with very cold temperatures we recommend using SELENIA PERFORMER
MULTIPOWER SAE 5W-30.
...
Air Conditioning (A/C)
The Air Conditioning (A/C) button allows the operator to manually activate or
deactivate the air conditioning system. When in A/C mode with the ATC set to a cool
temperature, dehumidified air flow ...