1999 GMC SUBURBAN Owner's Manual

3-12 Heating
The heater works best if you keep your windows
closed while using it. On cold days, use the HEATER
or VENT/HEAT setting with the temperature knob in
the red area.
On cold days, approximately 32
F (
-0
C) or lower, if
your vehicle is equipped with an automatic transmission,
you may experience differences in how the transmission
shifts until the engine is warm. This feature automatically
reduces the time it takes for the engine to reach normal
operating temperature and shortens the time it takes the
heater to reach full output.
If you use the engine coolant heater before starting your
engine in cold weather, 20
F (
-8
C) or lower, the
heating system will produce warmer air faster to heat the
passenger compartment.
The use of an engine coolant heater also reduces the
time it takes for the engine to reach normal operating
temperature. For more information, see ªEngine Coolant
Heaterº in the Index.
Defogging and Defrosting
On cool, humid days, use DEFOG to keep the
windshield and side windows clear. Use DEFROST to
remove fog or ice from the windshield in extremely
humid or cold conditions. Use DEFROST with the
temperature knob toward the red area and the fan
control turned all the way to the right.
Rear Window Defogger (If Equipped)
If you see lines running across the rear window, you
have a rear window defogger. The lines warm the glass.
To turn on the rear window
defogger, press this button
located next to the fan
control knob.
The rear window defogger
will only work if the
ignition is in RUN. For best
results, clear the window
of as much snow or ice
as possible first.

3-13
The defogger will shut itself off after several minutes.
If you need additional warming time, press the button
again. You can turn the defogger off at any time by
pressing the button.
If your vehicle is equipped with heated outside mirrors,
the rear window defogger button will also activate the
heated outside mirrors.
Do not attach a temporary vehicle license, tape or decals
across the defogger grid on the rear window.
NOTICE:
Don't use a razor blade or something else sharp
on the inside of the rear window. If you do, you
could cut or damage the warming grid, and the
repairs wouldn't be covered by your warranty.
Ventilation System
For mild outside temperatures when little heating or
cooling is needed, use VENT to direct outside air
through your vehicle. Air will flow through the
instrument panel outlets.
Your vehicle's ventilation system supplies outside air
to the inside of your vehicle when it is moving. With
the side windows closed, air will flow into the front
air inlet grilles, through the vehicle, and out the air
exhaust valves.
Outside air will also enter the vehicle when the heater
or the air conditioning fan is running, unless you have
the RECIRCULATION button pushed in. For more
information on the RECIRCULATION button,
see ªAir Conditioningº earlier in this section.

3-14
Your vehicle has air outlets
in the center and on the
sides of the instrument
panel and also may be
equipped on the headliner.
You can turn the outlets from side
-to-side or up
and down to direct the flow of air. The left driver
and passenger outlets on vehicles equipped with air
conditioning have shut off knobs. Turn the knob to
the left to shut off air flow, to the right to allow air flow.
When you close an outlet, it will increase the flow of air
coming out of any outlets that are open. The center
outlet does not completely shut off airflow.Ventilation Tips

Keep the hood and front air inlet free of ice, snow or
any other obstruction (such as leaves). The heater
and defroster will work far better, reducing the
chance of fogging the inside of your windows.

When you enter a vehicle in cold weather, turn the
blower fan all the way to the right for a few moments
before driving. This helps clear the intake ducts of
snow and moisture, and reduces the chance of
fogging the inside of your windows.

Keep the air path under the front seats clear of
objects. This helps air to circulate throughout
your vehicle.

The use of hood air deflectors may adversely
affect the performance of the heating and air
conditioning system.

3-15
Audio Systems
Your audio system has been designed to operate easily
and give years of listening pleasure. You will get the
most enjoyment out of it if you acquaint yourself with it
first. Find out what your audio system can do and how
to operate all its controls, to be sure you're getting the
most out of the advanced engineering that went into it.
Setting the Clock for Systems with
SET Button
Press SET. Within five seconds, press and hold the
SEEK right arrow until the correct minute appears on
the display. Press and hold the SEEK left arrow until
the correct hour appears on the display.
Setting the Clock for Systems with HR
and MN Buttons
Press and hold HR until the correct hour appears on
the display. Press and hold MN until the correct minute
appears on the display. To display the clock with the
ignition off, press RECALL or HR/MN and the time
will be displayed for a few seconds. There is an initial
two
-second delay before the clock goes into the
time
-set mode.
AM-FM Stereo
Playing the Radio
VOLUME: This knob turns the system on and off and
controls the volume. To increase volume and turn the radio
on, turn the knob clockwise. Turn it counterclockwise to
decrease volume and turn the radio off.
RECALL: Display the time with the ignition off by
pressing the recall knob. When the radio is playing,
press this knob to recall the station frequency.
Finding a Station
AM
-FM: Press the lower knob to switch between
AM and FM. The display shows your selection.
TUNE: Turn the lower knob to tune in radio stations.

3-16
SEEK: Press the right arrow to tune to the next higher
station and the left arrow to tune to the next lower
station and stay there.
SCAN:Select either AM, FM1 or FM2 mode and
press both SEEK buttons to listen to a few seconds of
each radio station. SCAN will light up on the display.
The radio will automatically SCAN to the next higher
station, play that station for a few seconds, then SCAN
to the next higher station. Press VOLUME or both
SEEK buttons to stop scanning.
PUSHBUTTONS: The four numbered pushbuttons let
you return to your favorite stations. You can set up to
14 stations (seven AM and seven FM). Just:
1. Turn the radio on.
2. Press AM
-FM to select the band.
3. Tune in the desired station.
4. Press SET. (SET will appear on the display.)
5. Press one of the four pushbuttons within five
seconds. Whenever you press that numbered button,
the station you set will return.
6. Repeat the steps for each pushbutton.In addition to the four stations already set, up to three
more stations may be preset on each band by pressing
two adjoining buttons at the same time. Just:
1. Tune in the desired station.
2. Press SET. (SET will appear on the display.)
3. Press two adjoining buttons at the same time,
within five seconds. Whenever you press the same
two buttons, the station you set will return.
4. Repeat the steps for each pair of pushbuttons.
Setting the Tone
BASS: Slide this lever up or down to increase or
decrease bass.
TREB: Slide this lever up or down to increase or
decrease treble. If a station is weak or noisy, you may
want to decrease the treble.
Adjusting the Speakers
BAL: Turn the control behind the upper knob to move
the sound to the left or right speakers. The middle
position balances the sound between the speakers.
FADE: Turn the control behind the lower knob to move
the sound to the front or rear speakers. The middle
position balances the sound between the speakers.

3-17 AM-FM Stereo with Cassette Tape Player
(If Equipped)
Playing the Radio
VOLUME: This knob turns the system on and off and
controls the volume. To increase volume and turn the radio
on, turn the knob clockwise. Turn it counterclockwise to
decrease volume and turn the radio off.
RECALL: Display the time with the ignition off by
pressing this knob. When the radio is playing, press this
knob to recall the station frequency.Finding a Station
AM
-FM: Press the lower knob to switch between
AM, FM1 and FM2.
TUNE: Turn the lower knob to tune in radio stations.
SEEK: Press the right arrow to tune to the next
higher station and the left arrow to tune to the next
lower station.
PUSHBUTTONS: The four numbered pushbuttons let
you return to your favorite stations. You can set up to
21 stations (seven AM, seven FM1 and seven FM2). Just:
1. Turn the radio on.
2. Press AM
-FM to select the band.
3. Tune in the desired station.
4. Press SET. (SET will appear on the display.)
5. Press one of the four pushbuttons within five
seconds. Whenever you press that numbered button,
the station you set will return.
6. Repeat the steps for each pushbutton.

3-18
In addition to the four stations already set, up to three
more stations may be preset on each band by pressing
two adjoining buttons at the same time. Just:
1. Tune in the desired station.
2. Press SET. (SET will appear on the display.)
3. Press two adjoining buttons at the same time,
within five seconds. Whenever you press the same
two buttons, the station you set will return.
4. Repeat the steps for each pair of pushbuttons.
P.SCAN: Select either AM, FM1 or FM2 mode and
press both SEEK buttons to scan through each of your
preset stations. The system will scan through and play
each preset station stored on your pushbuttons for a few
seconds. Press either SEEK button or RECALL to stop
scanning through the preset stations.
Setting the Tone
BASS: Slide this lever up or down to increase or
decrease bass.
TREB: Slide this lever up or down to increase or
decrease treble. If a station is weak or noisy, you may
want to decrease the treble.Adjusting the Speakers
BAL: Turn the control behind the upper knob to move
the sound to the left or right speakers. The middle
position balances the sound between the speakers.
FADE: Turn the control behind the lower knob to move
the sound to the front or rear speakers. The middle
position balances the sound between the speakers.
Playing a Cassette Tape
Your tape player is built to work best with tapes that
are up to 30 to 45 minutes long on each side. Tapes
longer than that are so thin they may not work well in
this player.
Once the tape is playing, use the knobs for VOLUME,
BAL, FADE, BASS and TREB just as you do for
the radio.
REV: Press the SEEK left arrow to reverse the
cassette tape. Press the SEEK right arrow to stop
reversing the tape.
FWD: Press the SEEK right arrow to advance the
cassette tape. Press the SEEK left arrow to stop
forwarding the tape.
RECALL: Press this knob to switch tape sides.

3-19
EJECT: Press this button to remove the tape or stop
the tape and play the radio.
CLN: If this message appears on the display, the cassette
tape player needs to be cleaned. It will still play tapes, but
you should clean it as soon as possible to prevent damage
to the tapes and player. See ªCare of Your Cassette Tape
Playerº in the Index. After you clean the player, press and
hold EJECT for five seconds to reset the CLN indicator.
The radio will display
--- to show the indicator was reset.
CD Adapter Kits
It is possible to use a portable CD player adapter kit
with your cassette tape player after activating the bypass
feature on your tape player.
To activate the bypass feature, use the following steps:
1. Turn the radio on.
2. Insert the adapter into the cassette slot.
3. Within five seconds, press and hold the REV and
FWD buttons at the same time for three seconds.
The tape symbol on the display will flash, showing
that the cut tape detection feature is no longer active.
This override routine will remain active until EJECT
is pressed.
AM-FM Stereo with Cassette Tape Player
and Automatic Tone Control (If Equipped)
Playing the Radio
PWR
-VOL: Press this knob to turn the system on
and off. To increase volume, turn the knob clockwise.
Turn it counterclockwise to decrease volume. The knob
is capable of being rotated continuously.
RECALL: Display the time with the ignition off by
pressing this button. When the radio is playing, press
this button to recall the station frequency.