GM Service Manual Online
For 1990-2009 cars only

The following components, when used in combination, determine the blower speed:

    â€¢ The blower resistor.
    â€¢ The blower switch.

The blower resistor consists of 3 resistors located in the same housing.

With the blower switch in LO, the following actions occur:

    â€¢ The blower circuit uses all 3 resistors.
    â€¢ The blower motor runs at the lowest speed.

With the blower switch in M1, the following actions occur:

    â€¢ Two of the resistors are in use.
    â€¢ The blower motor runs faster.

With the blower switch in M2, the following actions occur:

    â€¢ Only one of the resistors is in use.
    â€¢ The blower motor runs even faster.

With the blower switch in HI, the following actions occur:

    â€¢ None of the resistors are in use.
    â€¢ The blower motor runs at maximum speed.