Drivers of 2006-09 Mazda3 and Mazda5 models may complain that their air conditioning system stops blowing cool air and/or that the volume of air through the HVAC registers diminishes while driving on the open road for an extended period of time in high humidity conditions.
According to Mazda, two likely causes for the troubles are defects in the evaporator's temperature sensor combined with uneven airflow across the evaporator's surface. Installing a short harness with a built-in resistor, part #BPY1-61-545A, in series with the temp sensor and a new-design cabin air filter, part #BP8P-61-J6X, should eliminate the A/C system issues. For your information, the new harness corrects the temp sensor abnormalities. The updated cabin filter includes a deflector plate to even out the airflow across the heat exchanger.