1999 GMC C-SERIES heater

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3-2
Comfort Controls
Standard Comfort Controls
If your vehicle does not have air conditioning, this is
what your comfort controls will look like.
Function Lever
The top lever can be moved to three different heating
functions. If you place the lever between positions, it
will send air out both vents.
VENT: The air comes out at the vents on your
instrument panel and at your front side windows.
HEATER: Heated air comes out near the floor.
This is the best setting for cold weather.
DEFOG: This setting operates the defogger.
Heated air comes out near the windshield. Use this when
fog or ice is on the windshield.
Temperature Lever
The bottom lever lets you select the temperature of the
air flowing into your vehicle. Move the lever to the plus
symbol for warmer air. Move the lever to the minus
symbol for cooler air.
If your engine is equipped with an engine coolant heater,
you can use it during initial start
-up in cold weather
(20
F (
-8
C) or lower) to help heat the passenger
compartment faster. See ªEngine Coolant Heaterº in
the Index.
Fan Knob
The fan knob has four positions. To increase airflow,
turn the knob toward the plus symbol. To decrease
airflow, turn it toward the minus symbol.
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3-3 Optional Comfort Controls (If Equipped)
If your vehicle has air conditioning, your comfort
controls will look like this.
Your system has a lighted display showing each system
when it is operating. During normal operation, all the
lights won't come on at the same time. Only the ones
displaying the current settings will light.
Temperature Selector Bar
The bar under your system display lets you select the
temperature of the air coming into the passenger area of
your vehicle. Press COLD for cooler air and press HOT
for warmer air. Release the bar when the system reaches
the temperature you want. The temperature is shown on
the display by an arrow moving between C and H.
If your engine is equipped with an engine coolant heater,
you can use it during initial start
-up in cold weather
(20
F (
-8
C) or lower) to help heat the passenger
compartment faster. See ªEngine Coolant Heaterº in
the Index.
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3-4
Left Blend Button
The airflow can be blended between the two positions.
To blend between the positions, press the side of the
button showing the area where you would like more
airflow. The system will automatically begin to blend
toward the position chosen. To stop the system between
positions, just press the same side of the button again.
VENT: Press the top of the button and all of the
airflow will come through the instrument panel vents.
HEATER: Press the bottom of this button and all
of the airflow will come through the floor outlet.
Right Blend Button
The airflow can be blended between the two positions.
To blend between positions, press the side of the button
showing the area where you would like more airflow.
The system will automatically begin to blend toward the
position chosen. To stop the system between positions,
just press the same side of the button again.
DEFOG: This setting operates the defogger. Air
comes out near the bottom of the windshield and at your
front side windows.
HEATER: Press the bottom of this button and
heated air comes out near the floor.A/C Button
Press the A/C button to turn your air conditioner on and
off. The A/C symbol will light on your display, and air
will come out of your instrument panel vents. The fan
will automatically be set on LOW.
MAX Button
If you press the MAX button, the air in your vehicle will
be recirculated. With the air conditioner on, MAX will
give you maximum cooling. It can also be used in all
modes to help keep dust out of your vehicle. When
MAX is selected, REC will light on the display.
Fan Control Button
This button is in the upper passenger's side corner of
your system control panel. The fan has four settings:
low, medium low, medium high and high. Press the top
of the button with the plus symbol to increase airflow.
Press the bottom of the button with the minus symbol to
decrease airflow. The setting you select is shown on
your display as LOW, MED, HI or OFF.
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3-5
OFF
Press this button to turn the air conditioning/heating
system off. Pressing OFF will erase the present mode of
operation from the system's memory. Outside air will
still come out of the heater outlet whenever the vehicle
is moving forward.
If the OFF button is pressed, you must press A/C,
MAX or one of the BLEND buttons to turn the system
back on.
Air Conditioning
When you first turn on your vehicle's air conditioning,
open the windows long enough to clear the vehicle of
hot air, then close them. Using the MAX button can also
help. See ªMAX Buttonº earlier in this section for
more information.
For normal cooling on hot days, use A/C with the
temperature selector toward C.
When you press the A/C button to turn the air
conditioner off, the system will operate in the vent
mode. When you turn the air conditioner back on, the
system will operate in the mode you last selected unless
the OFF button was pressed.If your air conditioner develops high system pressure, it
will automatically go into the MAX mode and REC will
light on your display. The A/C system will remain in the
MAX mode, even if you press the MAX button, until
system pressure returns to a normal level.
Heating
On cold days, use HEATER with the temperature
selector all the way toward H. When the inside of the
vehicle has reached a comfortable temperature, maintain
it by using the temperature selector bar.
If your vehicle is equipped with a diesel engine, and the
engine has been idling for a long time when it's cold
outside, your heater may blow out cool air. This is
normal. When you increase the engine speed under load,
your heater should blow out warmer air. If it doesn't,
your coolant level may be low. See ªEngine Coolantº in
the Index to check your coolant level.
While idling your diesel engine, you can use the MAX
button to recirculate the air in the cab to help maintain
interior heat. This will preserve engine coolant temperature
and cab heat when idling cannot be avoided.
Using the MAX button while driving is not recommended
because interior window fogging can result.
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3-6 Defogging
Use DEFOG, along with the HEATER setting, when
there is fog or ice on the windshield. This will direct
airflow toward the windshield and front side windows.
Set the temperature selector toward H and the fan
control at a comfortable level. When the windshield is
clear, use the temperature selector bar and the fan
control button to maintain a comfortable
temperature level.
Ventilation System
Air comes into your vehicle in one of two ways: power air
or ram air. Power air means bringing outside air into the
cab through the air intake, using the blower fan. Fresh air
can be drawn in when the vehicle is stationary or moving
at low speed. Air comes in through four vents in the
instrument panel and is exhausted through the vents and
pressure relief valves in the doors and door pillars. Power
ventilation means an increased supply of fresh air is
brought into the cab interior without having to open the
windows, especially during inclement weather.
Ram air is forced into the cab through the air intake in
the cowl by the vehicle's forward motion. This air is
controlled by two vent air handles under the instrument
panel. Air is directed through the ventilation ducts to the
floor. Ram air provides good airflow into the cab at
normal road speeds.
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3-7
Ventilation Tips

Keep the hood and front air inlet free of ice, snow or
any other obstruction (such as leaves). The heater
and defogger 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 to high for a few moments before driving
off. 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 seats clear of objects.
This helps air to circulate throughout your vehicle.
The air vents are located in the center and on the sides of
your instrument panel. You can move the vents to direct
the flow of air or close the vents altogether. When you
close a vent, it will increase the flow of air coming out
of any vents that are open.
If your vehicle does not have air conditioning, there are
air vent controls located below the instrument panel.Audio Systems
Your Delco Electronics 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 Delco
Electronics 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
While pressing the SET button, press the UP button
until the correct hour appears on the display and the
DOWN button until the correct minute appears on the
display. If you press and hold the UP/DOWN button,
hours or minutes will advance rapidly.
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4-27

Tie a red cloth to your mirror arm to alert police that
you've been stopped by the snow.

Put on extra clothing or wrap a blanket around you.
If you have no blankets or extra clothing, make body
insulators from newspapers, burlap bags, rags, floor
mats
-- anything you can wrap around yourself or
tuck under your clothing to keep warm.
You can run the engine to keep warm, but be careful.
CAUTION:
Snow can trap exhaust gases under your vehicle.
This can cause deadly CO (carbon monoxide) gas
to get inside. CO could overcome you and kill
you. You can't see it or smell it, so you might not
know it is in your vehicle. Clear away snow from
around the base of your vehicle if any is blocking
your exhaust pipe. And check around again from
time to time to be sure snow doesn't collect there.
Open a window just a little on the side of the
vehicle that's away from the wind. This will help
keep CO out.
Run your engine only as long as you must. This saves
fuel. When you run the engine, make it go a little faster
than just idle. That is, push the accelerator slightly. This
uses less fuel for the heat that you get and it keeps the
battery (or batteries) charged. You will need a
well
-charged battery (or batteries) to restart the vehicle,
and possibly for signaling later on with your headlamps.
Let the heater run for a while.
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5-19 If No Steam Is Coming From Your Engine
If you get an engine overheat warning but see or hear no
steam, the problem may not be too serious. Sometimes
the engine can get a little too hot when you:

Climb a long hill on a hot day.

Stop after high
-speed driving.

Idle for long periods in traffic.
If you get the overheat warning with no sign of steam,
try this for a minute or so:
1. If you have an air conditioner and it's on, turn it off.
2. Turn on your heater to full hot at the highest fan
speed and open the window as necessary.
3. If you're in a traffic jam, shift to NEUTRAL (N);
otherwise, shift to the highest gear while
driving
-- DRIVE (D) for automatic transmissions.
4. If climbing a hill, downshift to raise engine and
fan speeds.If you no longer have the overheat warning, you can
drive. Just to be safe, drive slower for about 10 minutes.
If the warning doesn't come back on, you can
drive normally.
If the warning continues, pull over, stop, and park your
vehicle right away.
If there's still no sign of steam, push down the
accelerator until the engine speed is about twice as fast
as normal idle speed for at least three minutes while
you're parked. If you still have the warning, turn off the
engine and get everyone out of the vehicle until it
cools down.
You may decide not to lift the hood but to get service
help right away.
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