Air Speed

The blower motor forces air to circulate within the vehicles interior. The vehicle operator determines the blower motors speed by placing the blower motor switch in a desired speed position. The blower motor will only operate if the blower motor switch is in any position other than OFF, and the ignition switch is in the RUN position. Once a blower speed is selected, the blower speed remains constant until a new speed is selected.

As the requested blower speed increases, the following conditions occur:

• The HVAC control module increases the amount of time that the blower motor speed control circuit is modulated to ground.
• The voltage and duty cycle, measured between the blower motor speed control circuit and ground, decrease.

As the requested blower speed decreases, the following conditions occur:

• The HVAC control module decreases the amount of time that the blower motor speed control circuit is modulated to ground.
• The voltage and duty cycle, measured between the blower motor speed control circuit and ground, increase.