1. Remove the climate control unit.
2. Inspect for continuity between the fan switch terminals using an ohmmeter.


Climate control unit inspection
Defroster switch inspectionMazda 6 Service Manual: Scheduled Maintenance (U.S.A., Canada, and Puerto Rico)
Follow Schedule 1 if the vehicle is operated mainly where none of the following
conditions (severe driving conditions) apply.
Repeated short-distance driving
Driving in dusty conditions
Driving with extended use of brakes
Driving in areas where salt or other corrosive materials are used
...
Mazda 6 Service Manual: Identification Numbers
Vehicle Information Labels
Vehicle Identification Number
The vehicle identification number legally identifies your vehicle. The number
is on a plate attached to the cowl panel located on the left corner of the dashboard.
This plate can easily be seen through the windshield.
Motor Vehicle Sa ...