Blower Speed Selector Switch

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The HVAC control assembly applies voltage to the blower motor control circuit that corresponds to the selected blower speed. The resistors and the blower motor are in a series circuit. The following list represents the number of resistors in series with the blower motor per particular speed request:

Low speed - (3) resistors.
Medium (1) speed - (2) resistors.
Medium (2) speed - (1) resistor.

When the operator requests High speed, the HVAC control assembly applies voltage to the blower motor relay through the high blower motor control circuit. The voltage energizes the blower motor relay, connecting the blower motor to battery voltage. See Fig 1.

Fig 1: Main HVAC Control Assembly Functions

Courtesy of GENERAL MOTORS CORP.