GMC 1999 Suburban, Owner'S Manual, Page: 156 / 424

yellow blue
3-4
DEFROST: This setting directs air toward
the windshield.
Rear Air Conditioning and Heating Systems
(If Equipped)
If your vehicle has one of these systems, you can
increase and decrease the airflow at the rear vents.
Depending on the system you have and the setting
selected, you can send cooled or heated air to the rear of
the vehicle.
Rear Air Conditioning (Without Rear Heater)
(If Equipped)
If your vehicle has rear air conditioning (without rear
heater), the controls are located above the front and
second seats. The front and rear overhead controls let
you increase and decrease the airflow at the rear vents.
To operate the rear air conditioning system, the front air
conditioning system must be on. With the front air
conditioning system off, the rear system controls can be
used only to circulate air in the rear of the vehicle.
To operate the rear system using the front control, just
turn the knob to the blower position you want.