light GMC SUBURBAN 1999 Workshop Manual

3-6
Mode Knob - Automatic Operation
The right knob on the control panel allows you to
choose the direction of air delivery. When the system is
set for automatic operation, sensors will control the air
delivery mode. Air will come primarily from the floor or
instrument panel outlets, with some air directed to the
windshield to prevent fogging.
When the system is in AUTO mode, the air conditioning
light will turn on, and the recirculation and outside air
lights turn off. With the system in full auto control
(both the fan and mode knobs in AUTO), you still
have the ability to override any function. However,
continually overriding the outside air or the A/C
compressor will limit the ability of the system to cool
the vehicle quickly.
If you push a button for a function which is not
available, the light next to that button will flash three
times to alert you that it's not available.
To find your comfort zone, start with the 74
F (23
C)
setting and allow about 20 minutes for the system to
adjust the temperature if necessary.With the automatic setting, the air conditioning
compressor automatically cycles when needed to cool the
air. In cold weather, when the system senses the need
for heat, the airflow will be directed out the floor outlets.
As the interior temperature approaches a desired setting,
the blower speed will decrease. To maintain interior
comfort, the airflow will adjust between the instrument
panel air outlets and floor outlets. On bright sunny days
in cool weather, the airflow may come out of the air
conditioning and floor outlets (bi
-level mode) to maintain
comfort and prevent stuffiness.
To avoid blowing cold air in cold weather, the system
will delay turning on the fan until warm air is available.
The length of delay depends on the outside air
temperature, engine coolant temperature or the time
since the engine was last started. As the coolant warms
up, the blower fan speed will gradually increase and
air will flow from the heater outlets, with some airflow
to the windshield to prevent fogging under most
normal conditions.
Be careful not to put anything over the solar sensor
located around the center of the instrument panel.
This sensor is used by the automatic system to
regulate temperature.

3-7
Mode Knob - Manual Operation
The right knob on the control panel allows you to
choose the direction of air delivery.
You can choose to set the climate control system
operations yourself, or let the system work for you
by placing the system in AUTO mode. See ªMode
Knob
- Automatic Operationº earlier in this section.
PANEL: This setting directs most of the air
through the instrument panel outlets and a small amount
through the floor outlets.
BI-LEVEL: Air is delivered through the heater
floor outlets as well as the instrument panel outlets.
HEATER: This setting directs most of the
warmed air through the heater floor outlets and some
air through the windshield defroster outlets.
BLEND: Airflow is divided equally between the
heater floor outlet and the windshield defroster outlets.
The air conditioning compressor may run to dehumidify
the air to prevent window fogging.
DEFROST: This setting directs most air through
the windshield defroster outlets and some through the
heater outlets. The air conditioning compressor may
run to dehumidify the air to prevent window fogging.
OUTSIDE AIR: Press this button to force
the system to use outside air. Press it again to close off
the outside air.
Pressing the OUTSIDE AIR button will cancel the
RECIRCULATION button.
RECIRCULATION: Press this button to limit
the amount of fresh air entering your vehicle. This is
helpful when you are trying to limit odors entering your
vehicle or attempting to quickly cool down the interior.
In the AUTO mode, the system will use recirculation
as necessary to cool the air. Pressing the recirculation
button will change the operation to a manual mode and
the air will recirculate non
-stop. Press this button again
to turn off the recirculation feature.
RECIRCULATION may be selected with the fan control
in OFF to limit odors, outside air and dust from entering
your vehicle.
Pressing the RECIRCULATION button will cancel the
OUTSIDE AIR button.
A/C: Press this button to turn the air conditioning
on and off. The system will cool and dehumidify the air
inside the vehicle when the A/C light is on. When in AUTO,
the A/C is automatically engaged when necessary.

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.

3-20
SCV: Your system has a feature called
Speed
-Compensated Volume (SCV). With SCV,
your audio system adjusts automatically to make up for
road and wind noise as you drive. Set the volume at the
desired level. Turn the control ring behind the upper
knob clockwise to adjust the SCV. Then, as you drive,
SCV automatically increases the volume, as necessary,
to overcome noise at any particular speed. The volume
level should always sound the same to you as you drive.
If you don't want to use SCV, turn the control all the
way down. Each notch on the control ring allows for
more volume compensation at faster vehicle speeds.
Finding a Station
AM
-FM: Press this button to switch between AM,
FM1 and FM2. The display will show your selection.
TUNE: Press this knob lightly so it extends. Turn it to
choose radio stations. Push the knob back into its stored
position when you're not using it.
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. The sound will mute
while seeking.SCAN: Press and hold SEEK for two seconds until
SCAN appears on the display. SCAN allows you to
listen to stations for a few seconds. The receiver will
continue to scan and momentarily stop at each station
until you press the button again. The sound will mute
while scanning.
PUSHBUTTONS: The six numbered pushbuttons let
you return to your favorite stations. You can set up to
18 stations (six AM, six FM1 and six FM2). Just:
1. Turn the radio on.
2. Press AM
-FM to select the band.
3. Tune in the desired station.
4. Press AUTO TONE to select the setting you prefer.
5. Press and hold one of the six pushbuttons. The
sound will mute. When it returns, release the button.
Whenever you press that numbered button, the
station you set will return and the tone you selected
will be automatically selected for that button.
6. Repeat the steps for each pushbutton.

3-21
P.SCAN: The preset scan button lets you scan through
your favorite stations stored on your pushbuttons.
Select either the AM, FM1 or FM2 mode and then
press P. SCAN. It will scan through each station stored
on your pushbuttons and stop for a few seconds before
continuing to scan through all of the pushbuttons.
Press P. SCAN again or one of the pushbuttons to stop
scanning to listen to a specific preset station. P. SCAN
will light up on the display while in this mode. If one
of the stations stored on a pushbutton is too weak for
the location you are in, the radio display will show the
channel number (P1
-P6) for several seconds before
advancing to the next preset station.
Setting the Tone
BASS: Press lightly on this knob to release it from its
stored position. Turn the knob clockwise to increase bass
and counterclockwise to decrease bass. When the BASS
control is rotated, the AUTO TONE display will go blank.
TREB: Press lightly on this knob to release it from its
stored position. Turn the knob clockwise to increase
treble and counterclockwise to decrease treble. When
the TREB control is rotated, the AUTO TONE display
will go blank. If a station is weak or noisy, you may
want to decrease the treble.
Push these knobs back into their stored positions when
you're not using them.AUTO TONE: Press this button to select among the
six preset equalization settings and tailor the sound to
the music or voice being heard. Each time you press the
button, the selection will switch to one of the preset
settings of CLASSIC, NEWS, ROCK, POP, C/W
(Country/Western) or JAZZ. To return to the manual
mode, press and release this button until the AUTO
TONE display goes blank. This will return the tone
adjustment to the BASS and TREB controls. If a
BASS or TREB control is rotated, the AUTO TONE
display will go blank. Use PUSHBUTTONS to program
AUTO TONE.
Adjusting the Speakers
BAL: Press lightly on this knob to release it from its
stored position. Turn the control clockwise to adjust
sound to the right speakers and counterclockwise to
adjust sound to the left speakers. The middle position
balances the sound between the speakers.
FADE: Press lightly on this knob to release it from its
stored position. Turn the control clockwise to adjust the
sound to the front speakers and counterclockwise for the
rear speakers. The middle position balances the sound
between the speakers.
Push these knobs back into their stored positions when
you're not using them.

3-23
AM-FM: Press this button to switch from a tape to
the radio.
TAPE AUX: Press this button to return to the tape
player when playing the radio. The lighted arrow will
appear and show the direction of play when a tape is in
the active mode.
EJECT: Press this button to remove the tape. The
radio will now play. EJECT can be used with either the
ignition or radio off. To load a cassette tape with the
ignition or radio off, press EJECT before loading
the cassette.
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 ignition to RUN or ACCESSORY.
2. Turn the radio off.
3. Press and hold the TAPE AUX button for five
seconds. The tape symbol on the display will flash
for two seconds, indicating the feature is active.
4. Insert the adapter into the cassette slot. It will
power up the radio and begin playing.
This override routine will remain active until EJECT
is pressed.

3-24 AM-FM Stereo with Compact Disc 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 this knob clockwise.
Turn it counterclockwise to decrease volume. The knob
is capable of rotating 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.SCV: Your system has a feature called
Speed
-Compensated Volume (SCV). With SCV,
your audio system adjusts automatically to make up for
road and wind noise as you drive. Set the volume at the
desired level. Turn the control ring behind the upper
knob clockwise to adjust the SCV. Then, as you drive,
SCV automatically increases the volume, as necessary,
to overcome noise at any particular speed. The volume
level should always sound the same to you as you drive.
If you don't want to use SCV, turn the control all the
way down. Each notch on the control ring allows for
more volume compensation at faster vehicle speeds.
Finding a Station
AM
-FM: Press this button to switch between AM,
FM1 and FM2. The display will show your selection.
TUNE: Press this knob lightly so it extends. Turn it to
choose radio stations. Push the knob back into its stored
position when you're not using it.
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. The sound will mute
while seeking.

3-25
SCAN: Press and hold SEEK for two seconds until
SCAN appears on the display. SCAN allows you to
listen to stations for a few seconds. The receiver will
continue to scan and momentarily stop at each station
until you press the button again. The sound will mute
while scanning.
PUSHBUTTONS: The six numbered pushbuttons let
you return to your favorite stations. You can set up to
18 stations (six AM, six FM1 and six FM2). Just:
1. Turn the radio on.
2. Press AM
-FM to select the band.
3. Tune in the desired station.
4. Press AUTO TONE to select the setting you prefer.
5. Press and hold one of the six pushbuttons. The
sound will mute. When it returns, release the button.
Whenever you press that numbered button, the
station you set will return and the tone you selected
will be automatically selected for that button.
6. Repeat the steps for each pushbutton.P.SCAN: The preset scan button lets you scan through
your favorite stations stored on your pushbuttons.
Select either the AM, FM1 or FM2 mode and then
press P.SCAN. It will scan through each station stored
on your pushbuttons and stop for a few seconds before
continuing to scan through all of the pushbuttons.
Press P.SCAN again or one of the pushbuttons to stop
scanning to listen to a specific stored station. P.SCAN
will light up on the display while in this mode. If one
of the stations stored on a pushbutton is too weak for
the location you are in, the radio display will show the
channel number (P1-P6) for several seconds before
advancing to the next preset station.
Setting the Tone
BASS: Press lightly on this knob to release it from its
stored position. Turn the knob clockwise to increase bass
and counterclockwise to decrease bass. When the BASS
control is rotated, the AUTO TONE display will go blank.
TREB: Press lightly on this knob to release it from its
stored position. Turn the knob clockwise to increase
treble and counterclockwise to decrease treble. When
the TREB control is rotated, the AUTO TONE display
will go blank. If a station is weak or noisy, you may
want to decrease the treble.
Push these knobs back into their stored positions when
you're not using them.

3-26
AUTO TONE: Press this button to select among the
six preset equalization settings and tailor the sound to
the music or voice being heard. Each time you press the
button, the selection will switch to one of the preset
settings of CLASSIC, NEWS, ROCK, POP, C/W
(Country/Western) or JAZZ. To return to the manual
mode, press and release this button until the AUTO
TONE display goes blank. This will return the tone
adjustment to the BASS and TREB controls. If a
BASS or TREB control is rotated, the AUTO TONE
display will go blank. Use PUSHBUTTONS to program
AUTO TONE.
Adjusting the Speakers
BAL: Press lightly on this knob to release it from its
stored position. Turn the control clockwise to adjust
sound to the right speakers and counterclockwise to
adjust sound to the left speakers. The middle position
balances the sound between the speakers.
FADE: Press lightly on this knob to release it from its
stored position. Turn the control clockwise to adjust the
sound to the front speakers and counterclockwise for the
rear speakers. The middle position balances the sound
between the speakers.
Push these knobs back into their stored positions when
you're not using them.Playing a Compact Disc
PWR: Press this knob to turn the system on. (You can
also turn the system on when you insert a compact disc
into the player with the ignition on.)
Insert a disc partway into the slot, label side up. The
player will pull it in. Wait a few seconds and the disc
should play. CD and a CD symbol will also appear on
the display. Anytime you are playing a CD, the letters
CD will be next to the CD symbol.
If the disc comes back out and ERR appears on the
display, it could be that:

You are driving on a very rough road. (The disc
should play when the road gets smoother.)

The disc is upside down.

It is dirty, scratched or wet.

It is very humid. (If so, wait about an hour
and try again.)

The disc player is very hot.
Press RECALL to make ERR go off the display.

3-28 Rear Seat Audio (If Equipped)
This feature allows rear seat passengers to listen to any
of the music sources including AM
-FM, automatic tone
control, cassette tapes and CDs. However, the rear seat
passengers can only control the music sources that the
front seat passengers are not listening to. For example,
rear seat passengers may listen to a cassette tape through
headphones while the driver listens to the radio through
the front speakers. The rear seat passengers have control
of the volume for each set of headphones. Be aware that
the front seat audio controls always override the rear
seat audio controls.
Note that this feature is intended for rear seat passengers.PWR: Press this button to turn the rear seat audio
system on or off. The rear speakers will be muted
when the power is turned on. You may operate the
rear seat audio functions even when the primary radio
power is off.
VOL: Press this knob lightly so it extends. Turn the
knob clockwise to increase volume and counterclockwise
to decrease volume. Push the knob back into its stored
position when you're not using it. The upper VOL knob
controls the upper headphone and the lower VOL knob
controls the lower headphone.
AM
-FM: Press this button to switch between AM, FM1
and FM2. If the front passengers are already listening to
AM
-FM, the rear seat audio controller will not switch
between the bands and cannot change the frequency.
SEEK: While listening to AM
-FM, press the up arrow
to tune to the next higher station and stay there. Press
the down arrow to tune to the next lower station and stay
there. The sound will mute while seeking. The SEEK
button is inactive if the AM
-FM mode on the front
radio is in use.
While listening to a cassette tape, press the up arrow to
hear the next selection on the tape. Press the down arrow
to go back to the previous selection. The SEEK button is
inactive if the tape mode on the front radio is in use.