brake light GMC C-SERIES 1999 Owner's Manual

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2-59
Air Brake System Warning Light
Vehicles with air brake systems have one brake system
warning light on the instrument panel.
The LOW AIR warning
light should come on, as a
check, whenever you start
the engine.
However, it is designed to come on, and stay on, when
brake reservoir pressure has dropped below 60 to 70 psi
(410 to 480 kPa).When this warning light comes on, you will also hear a
warning tone. If the warning light and tone come on
while you are driving, you should drive only as far as
the nearest point of safety and then stop the vehicle.
Here's a very important thing for you to know:
CAUTION:
If the LOW AIR warning light comes on and the
warning tone sounds, the vehicle can stop
suddenly and without further warning. This is
because the parking brake will come on if the
pressure falls below 40 to 45 psi (275 to 310 kPa).
You or others could be injured. If the LOW AIR
warning light comes on and the warning tone
sounds, stop as soon as you can. You won't
know how quickly the system is losing pressure,
so be aware that the parking brake may come
on suddenly.
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2-60 Apply Park Brake Warning Light (Option)
This light warns the driver
that the ignition has been
turned off without applying
the parking brake. The
warning light should come
on, as a check, when you
start the engine.
When it comes on, you will also hear a warning tone.
Leaving the vehicle in this condition could result in your
vehicle moving and will discharge the battery.
Parking Brake Warning Light
This light turns on as a
check when the engine is
first started and any time the
system needs adjustment or
there is a malfunction in the
electric/hydraulic parking
brake system.
When the SERVICE PARK BRAKE light comes on,
you will also hear a warning tone. If this light comes on,
have the system repaired immediately.
CAUTION:
If the SERVICE PARK BRAKE warning light
comes on and the warning tone sounds, your
vehicle can stop suddenly and without further
warning. You or others could be injured. If the
SERVICE PARK BRAKE warning light and the
warning tone come on, pull over to the side of the
road and apply the parking brake immediately.
Parking Brake Indicator Light
Vehicles with hydraulic or
air brakes have a parking
brake indicator light. When
the ignition is on, this light
will come on when you set
your parking brake.
The light will stay on if your parking brake doesn't
release fully.
This light should also come on when you turn the
ignition key to START. If it doesn't come on then, have
it fixed so it will be ready to remind you if the parking
brake is applied or hasn't released fully.
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2-61 Anti-Lock Brake System Warning Light
(Option)
With the anti-lock brake
system, this light will come
on when you start your
engine and it may stay on
for several seconds.
That's normal.
If the light stays on, or comes on when you're driving,
your vehicle needs service. If the PRIMARY BRAKE or
LOW AIR warning light isn't on, you still have brakes,
but you don't have the anti
-lock brake feature. If the
PRIMARY BRAKE and/or LOW AIR warning light is
on, you don't have anti
-lock brakes and there's a
problem with your regular brakes. See ªBrake System
Warning Lightº earlier in this section.
The anti
-lock brake system warning light should come
on briefly when you turn the ignition key to RUN. If the
light doesn't come on then, have it fixed so it will be
ready to warn you if there is a problem.
Engine Coolant Temperature Gage
Gasoline Engine Diesel Engine
This gage shows the engine coolant temperature. If
the gage pointer moves into the red area, your engine
coolant might have overheated and your engine may be
too hot. You should pull off the road, stop your vehicle
and turn off the engine as soon as possible.
See ªEngine Overheatingº in the Index. If you have a
Caterpillar

diesel engine, also see your Caterpillar

Operation & Maintenance Manual.
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2-69 Transmission Temperature Gage
(If Equipped)
If you have an automatic
transmission and this gage,
it is to the right of the dash
mounted shift lever, just to
the right of your
floor
-mounted shift lever or
on the lower portion of the
instrument panel to the right
of the steering wheel.
When your ignition is on, the gage shows the
temperature of the transmission oil. A reading in the
warning zone means you must stop driving and check
into the cause. One possible cause is a low oil level in
the transmission.
NOTICE:
If you drive when the transmission temperature
gage is in the warning zone, you can badly
damage the transmission.
Air Pressure Gage (If Equipped)
If your vehicle has air
brakes, this gage at the
center of your instrument
cluster shows the air
pressure for both your front
and rear brake systems.
If the needle on the gage indicates that the air pressure is
below 60 psi (415 kPa), the LOW AIR warning light
will come on. An alarm will also sound if this happens.
The yellow pointer shows the pressure available for the
front system, while the green pointer shows pressure for
the rear. There should be no more than 4 psi (28 kPa)
difference showing between the systems.
Don't drive until both pointers are showing at least
120 psi (830 kPa), so you'll have enough air if you need
to apply your brakes.
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4-7
Avoid needless heavy braking. Some people drive in
spurts
-- heavy acceleration followed by heavy
braking
-- rather than keeping pace with traffic. This
is a mistake. Your brakes may not have time to cool
between hard stops. Your brakes will wear out much
faster if you do a lot of heavy braking. If you keep pace
with the traffic and allow realistic following distances,
you will eliminate a lot of unnecessary braking. That
means better braking and longer brake life.
If your engine ever stops while you're driving, brake
normally but don't pump your brakes. If you do, the
pedal may get harder to push down. If your engine
stops, you will still have some power brake assist. But
you will use it when you brake. Once the power assist is
used up, it may take longer to stop and the brake pedal
will be harder to push.
Hydraulic Brake Systems
If your engine stops running, or if your primary brake
system stops working, your vehicle has a reserve power
assist system to help you slow down. Just slowly and
steadily apply the brake pedal until you can safely get
off the road. The pedal will seem harder to push down.
Don't pump the pedal; the system won't work well or at
all that way.You may find that the steering wheel seems hard to turn
when you're turning and braking at the same time. Also,
the PRIMARY BRAKE warning light may come on and
the warning tone may sound. This is normal because the
main hydraulic brake system and power steering both
use the power steering pump. If this ever happens, let up
on the brake pedal a little. When you let up on the brake
pedal in that situation, it lets the steering get a little
more help from the pump.
Anti-Lock Brakes (Option)
Your vehicle may have anti-lock brakes (ABS). ABS is
an advanced electronic braking system that will help
prevent a braking skid.
If your vehicle has anti-lock
brakes, this warning light on
the instrument panel will
come on briefly when you
start your vehicle.
When you start your engine and begin to drive away,
your anti
-lock brake system will check itself. You may
hear a momentary motor or clicking noise while this test
is going on. This is normal.
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4-8
If there's a problem with the anti-lock brake system, the
anti
-lock brake system warning light will stay on. See
ªAnti
-Lock Brake System Warning Lightº in the Index.
Here's how anti-lock works. Let's say the road is wet.
You're driving safely. Suddenly an animal jumps out in
front of you.
You slam on the brakes. Here's what happens with ABS.A computer senses that wheels are slowing down. If one
of the wheels is about to stop rolling, the computer will
separately work the brakes at each wheel.
The anti
-lock system can change the brake pressure
faster than any driver could. The computer is
programmed to make the most of available tire and
road conditions.
You can steer around the obstacle while braking hard.
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4-17
The heavier the rain, the harder it is to see. Even if your
windshield wiper blades are in good shape, a heavy rain
can make it harder to see road signs and traffic signals,
pavement markings, the edge of the road and even
people walking.
It's wise to keep your wiping equipment in good shape
and keep your windshield washer tank filled with
washer fluid. Replace your windshield wiper inserts
when they show signs of streaking or missing areas on
the windshield, or when strips of rubber start to separate
from the inserts.Driving too fast through large water puddles or even
going through some vehicle washes can cause problems,
too. The water may affect your brakes. Try to avoid
puddles. But if you can't, try to slow down before you
hit them.
CAUTION:
Wet brakes can cause accidents. They won't work
as well in a quick stop and may cause pulling to
one side. You could lose control of the vehicle.
After driving through a large puddle of water or
a vehicle wash, apply your brake pedal lightly
until your brakes work normally.
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4-31
Power Take-Off (PTO) (If Equipped)
Before using a PTO, refer to the body builder's or
operator's instructions.
To engage a PTO:
1. Make sure the vehicle is stopped.
2. Shift the transmission into NEUTRAL (N) or
PARK (P), if equipped.
3. The brake or clutch pedal must be pressed and
released once before PTO can be enabled. Do not
hold the brake or clutch pedal down.4. The cruise control switch must be in ON prior to
engaging the PTO switch to enable PTO operation.
This sets the PTO base engine idle at 1200 rpm.
5. Use SET/COAST to change the engine speed to the
lower preset value of 1400 rpm. Use
RESUME/ACCEL to change the engine speed to the
upper preset value of 1800 rpm. You may toggle
between upper and lower by moving the switch
between SET/COAST and RESUME/ACCEL.
The PTO will become inoperative when any of the
conditions are changed or the CHECK GAGES light
comes on.
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6-29 What to Use
To determine what kind of fluid to use, see
ªRecommended Fluids and Lubricantsº in the Index.
NOTICE:
When adding power steering fluid or making a
complete fluid change, always use the proper
fluid. Failure to use the proper fluid can cause
leaks and damage hoses and seals.
If your power steering fluid level is low, this can
cause the PRIMARY BRAKE or AUX BRAKE
warning lights to come on. If either light remains
on after you have added power steering fluid to
the proper level, then shut off the engine for
10 seconds. This should reset the brake warning
lights. If one or both lights stay on, though,
then see ªHydraulic Brake Warning Lightsº in
the Index.
Windshield Washer Fluid
What to Use
When you need windshield washer fluid, be sure to read
the manufacturer's instructions before use. If you will be
operating your vehicle in an area where the temperature
may fall below freezing, use a fluid that has sufficient
protection against freezing.
Adding Washer Fluid
Open the cap labeled WASHER FLUID ONLY.
Add washer fluid until the tank is full.
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6-32
CAUTION:
With the wrong kind of fluid in your brake
system, your brakes may not work well, or they
may not even work at all. This could cause a
crash. Always use the proper brake fluid.
NOTICE:

Using the wrong fluid can badly damage
brake system parts. For example, just a few
drops of mineral
-based oil, such as engine
oil, in your brake system can damage brake
system parts so badly that they'll have to be
replaced. Don't let someone put in the
wrong kind of fluid, and don't use DOT
-5
silicone brake fluid.
NOTICE: (Continued)
NOTICE: (Continued)

If you spill brake fluid on your vehicle's
painted surfaces, the paint finish can be
damaged. Be careful not to spill brake fluid
on your vehicle. If you do, wash it off
immediately. See ªAppearance Careº in
the Index.
Four-Wheel Disc Brakes (Hydraulic Only)
Your vehicle has four-wheel disc brakes.
Some driving conditions or climates may cause a brake
squeal when the brakes are first applied or lightly
applied. This does not mean something is wrong with
your brakes.
Brake linings should always be replaced as complete
axle sets.
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