The refrigerant specifications are indicated on a label attached to the inside of the engine compartment. Check the label before refilling the refrigerant. If the wrong type of refrigerant is used, it could result in a serious malfunction of the air conditioner.
For details, consult an Authorized Mazda Dealer.

Vent OperationMazda 6 Owners Manual: Dehumidifying (With air conditioner)
Operate the air conditioner in cool or cold weather to help defog the windshield
and side windows.
1. Set the mode selector dial to the desired position.
2. Set the air intake selector to the outside air position (indicator light turns
off).
3. Set the temperature control dial to the desired ...
Mazda 6 Owners Manual: Refrigerant pressure switch removal/installation
1. Remove the battery.
2. Discharge the refrigerant from the system. (See RECOVERY.) (See CHARGING.)
3. Loosen the refrigerant pressure switch using two spanners.
4. Remove in the order indicated in the table.
5. Install in the reverse order of removal.
Refrigerant Pressure Switch Installat ...