warning lights CHEVROLET CAMARO 1982 Repair Guide

GM – CAMARO 1982-1992 – Repair Guide (Checked by WxMax) 49
Upon release of the brake pedal, a spri
ng located inside the master cylinder
immediately returns the master cylinder pistons to the normal position. The
pistons contain check valv es and the master cylinder has compensating ports
drilled in it. These are uncovered as the pistons reach their normal position. The
piston check valves allow fluid to flow to ward the wheel cylinders or calipers as
the pistons withdraw. Then, as the return springs force the brake pads or shoes
into the released position, the excess fluid reservoir through the compensating
ports. It is during the time the pedal is in the released position that any fluid that
has leaked out of the syst em will be replaced through the compensating ports.
Dual circuit master cylinders employ tw o pistons, located one behind the other,
in the same cylinder. The primary pist on is actuated directly by mechanical
linkage from the brake peda l through the power booster. The secondary piston
is actuated by fluid tra pped between the two pistons. If a leak develops in front
of the secondary piston, it moves forward until it bottoms against the front of the
master cylinder, and the fluid trapped betw een the pistons will operate the rear
brakes. If the rear brakes develop a l eak, the primary piston will move forward
until direct contact with the secondary pi ston takes place, and it will force the
secondary piston to actuate the front brakes. In either case, the brake pedal
moves farther when the brakes are applied, and less braking power is available.
All dual circuit systems use a switch to wa rn the driver when only half of the
brake system is operational. This switch is usually located in a valve body which
is mounted on the firewall or the frame below the master cylinder. A hydraulic
piston receives pressure from both circui ts, each circuit's pressure being applied
to one end of the piston. When the pressures are in balance, the piston remains
stationary. When one circuit has a leak, however, the greater pressure in that
circuit during application of the brakes will push the piston to one side, closing
the switch and activating the brake warning light.
In disc brake systems, this valve body also contains a metering valve and, in
some cases, a proportioning valve. The metering valve keeps pressure fro\
m
traveling to the disc brakes on the front wheels until the brake shoes on the rear
wheels have contacted the drums, ensuri ng that the front brakes will never be
used alone. The proportioning va lve controls the pressure to the rear brakes to
lessen the chance of rear wheel lo ck-up during very hard braking.
Warning lights may be tested by depressi ng the brake pedal and holding it while
opening one of the wheel cyli nder bleeder screws. If this does not cause the
light to go on, substitute a new lamp , make continuity checks, and, finally,
replace the switch as necessary.
The hydraulic system may be checked for leaks by applying pressure to the
pedal gradually and steadily. If the pedal sinks very slowly to the floor, the
system has a leak. This is not to be conf used with a springy or spongy feel due
to the compression of air within the lin es. If the system leaks, there will be a
gradual change in the position of the pedal with a constant pressure.
Check for leaks along all lines and at wheel cylinders. If no external leaks are
apparent, the problem is inside the master cylinder.

GM – CAMARO 1982-1992 – Repair Guide (Checked by WxMax) 138
the ground side of the circuit) and
connect the positive lead to the
positive (+) side of the circuit (to t he power source or the nearest power
source). Note that the negative voltme ter lead will always be black and
that the positive voltmeter will alwa ys be some color other than black
(usually red).
• Ohmmeter - the ohmmeter is designed to read resistance (measured in
ohms) in a circuit or component. Mo st ohmmeters will have a selector
switch which permits the measurement of different ranges of resistance
(usually the selector swit ch allows the multiplication of the meter reading
by 10, 100, 1,000 and 10,000). Some ohmmeters are "auto-ranging"
which means the meter itself will dete rmine which scale to use. Since the
meters are powered by an internal battery, the ohmmeter can be used
like a self-powered test light. When the ohmmeter is connected, current
from the ohmmeter flows through the ci rcuit or component being tested.
Since the ohmmeter's internal resi stance and voltage are known values,
the amount of current flow throug h the meter depends on the resistance
of the circuit or component being test ed. The ohmmeter can also be used
to perform a continuity test for suspected open circuits. In using the
meter for making continuity checks, do not be concerned with the actual
resistance readings. Zero resistance, or any ohm reading, indicates
continuity in the circui t. Infinite resistance indi cates an opening in the
circuit. A high resistance reading w here there should be none indicates a
problem in the circuit. Checks for s hort circuits are made in the same
manner as checks for open circuits, ex cept that the circuit must be
isolated from both power and normal gr ound. Infinite resistance indicates
no continuity, while zero resi stance indicates a dead short.
WARNING - Never use an ohmmeter to check the resistance of a component or
wire while there is volt age applied to the circuit
• Ammeter - an ammeter measures the am ount of current flowing through
a circuit in units called amperes or amps. At normal operating voltage,
most circuits have a characteristic amount of amperes, called "current
draw" which can be measured usi ng an ammeter. By referring to a
specified current draw rating, then measuring the amperes and
comparing the two values, one can det ermine what is happening within
the circuit to aid in diagnosis. An open circuit, for example, will not allow
any current to flow, so the amme ter reading will be zero. A damaged
component or circuit will have an incr eased current draw, so the reading
will be high. The ammeter is always connected in series with the circuit\

being tested. All of the current that normally flows through the circuit
must also flow through the ammeter; if there is any other path for the
current to follow, the ammeter readi ng will not be accurate. The ammeter
itself has very little resistance to curr ent flow and, therefore, will not affect
the circuit, but it will measure current draw only when the circuit is closed
and electricity is flowing. Excessive current draw can blow fuses and
drain the battery, while a reduced current draw can cause motors to run \
slowly, lights to dim and other components to not operate properly.