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: System wiring diagram
ABS (ABS/TCS)
DSC
FOREWORD
Before performing the steps in Symptom Troubleshooting, perform the
On-board Diagnostic Inspection. To check the DTC, follow the DTC Inspection
steps.
...
Mazda 6 Service Manual: Recommendations for Shifting
Upshifting
For normal acceleration and cruising, Mazda recommends these shift points:
*1 Always observe local speed limit regulations.
Downshifting
When you must slow down in heavy traffic or on a steep upgrade, downshift before
the engine starts to overwork. This gives better acceleration w ...