I have noticed that nexro to the air-condition light, there's an ECO light. Very rarely I've notice that it was on but I haven't managed to understand the conditions under it's on. Is there a way to manually enable economy mode for a/c?

 

You have a JDM model, we don't get that light in North America, & can't help you.

S

 

While this is an old question but it may assist others in future

the eco mode as mentioned by stealthtl is available on jdm models. But also Australian delivered models. Unknown for uk models but also possibly a possibility.

like some other systems it’s shared with other Mazda models such as the 3 and 6.
it will reduce the aircon engine load during times of higher engine use.
it’s most noticeable during acceleration and will act as if the Ac is turned off or severely reduced, resulting in a noticeably quicker acceleration and throttle response.

to activate this mode the ambient outside temperature will need to be below 24 or 25 degrees Celsius (to be tested at a later date)
to engage eco mode, as displayed between the a/c and auto indicators on the central dash lcd, you will need to change air flow from recirculated to external airflow. (the button below mode on the Ac controls)
eco mode and auto can be used together.