Air Speed: Notes

The blower motor forces air to circulate within the vehicles interior. The vehicle operator determines the blower motors speed by placing the blower knob dial in a desired speed position or by selecting automatic operation. In manual operation, the blower has six speed selections. The HVAC control module may alter the blower motor speed due to compensating factors. In automatic operation, the HVAC control module will determine what blower speed is necessary in order to achieve or maintain a desired temperature. In manual and automatic operation, the blower speed temporarily reduces speed during transition between outlet modes.

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.