Chevrolet Equinox Service Manual: Rear Window Defogger Description and Operation

Rear Window Defogger System Components

The rear window defogger system consists of the following components:

HVAC Control ModuleRadio/HVAC ControlsRear Defogger RelayRear Defogger GridDriver Outside Rearview MirrorPassenger Outside Rearview Mirror40A FuseE17DOutside Rearview Mirror Glass - DriverE18Rear Defogger GridE17POutside Rearview Mirror Glass - PassengerA20Radio/HVAC ControlsK33HVAC Control Module

Rear Window Defogger Operation

The rear defog control system utilizes a single zone backlight design, driven witha single relay configuration. Additionally, up to two outside rear view mirrors canbe heated if required. A switch for the customer to control the system is providedwithin the radio/HVAC controls. Also included in the radio/HVAC controls is an indicatorto inform the customer with the current state of the system. The system is only operationalwhen engineis running or during remote start.

Pressing the heated rear window switch causes the radio/HVAC controls to send a serialdata message to the HVAC control module requesting rear window defog operation. TheHVAC control module upon receipt of the serial data message will provide voltage tothe coil side of the rear defogger relay, this will energize the relay causing therelay switch contacts to close allowing B+ voltage to flow through the rear defoggergrid control circuitto the rear defogger grid.

When the rear heated window switch is pressed and the engine is running, the reardefog control system will remain active for 10 minutes. After the initial cycle haslapsed, pressing the switch again will continue rear window defogger operation, butthe cycle will only last 5 minutes. The rear defog control system will function continuouslyif the vehicle speed is greater than 70 kilometers per hour (45 mph).

Heated Mirrors

The heated mirrors are also controlled through the rear defogger relay. Whenever therear window defogger is turned on battery voltage is supplied to the mirror heaterelements through the left and right mirror heater element control circuits.