GM Service Manual Online
For 1990-2009 cars only

Control Settings

System Response

Step

Mode Lever

Temp Control

Fan Switch

Blower Speed

Vent Outlet

Heater Outlet

Defrost Outlets

See Remark

Rear Seat Heat Duct

1

VENT

COLD

OFF

Off

No Air Flow

No Air Flow

No Air Flow

--

No Air

2

VENT

COLD

LOW TO HIGH

Low to High

Air Flow

No Air Flow

No Air Flow

B, F, H, J

No Air

3

HEAT

HOT

HIGH

High

No Air Flow

Air Flow

Minimum Air Flow

A, D, E

Air

4

DEFROST

HOT

HIGH

High

No Air Flow

Minimum Air Flow

Air Flow

A, G

Min Air

5

BI-LEVEL

HOT

HIGH

High

Air Flow

Air Flow

No Air Flow

A

Air

6

BLEND

HOT

HIGH

High

No Air Flow

Air Flow

Air Flow

A

Air

REMARK A: Engagement of the detent must be felt in each mode.

REMARK B: Progressive blower speed increase must occur between LO, M1, M2 and HI.

REMARK C: Listen for the reduction of air noise.

REMARK D: Inspect the temperature level for full travel (Hot or Cold).

REMARK E: Inspect for air flow at the side window defogger outlets.

REMARK F: The temperature from the vent outlets should be the same as the temperature outside of the vehicle.

REMARK G: The temperature from the defroster outlets should be above the temperature outside of the vehicle.

REMARK H: Barrels and vanes must hold their position with the fan on high.

Inspect all of the A/C outlets for the following conditions:

    • Barrel rotation
    • Vane operation

Perform each step of the functional test shown on the illustration as one total operation of the roll test with the following conditions in place:

    • The window is up.
    • The door is closed.

Note any discrepancies from the remarks listed below.