332 Auto Brakes
Figure 19-3. A parking brake warning light electrical circuit schematic. The circuit is open, the parking brake switch contacts have
not made contact. Note the brake fluid level switch in the master cylinder. This switch may also turn on the warning light when the
sensor detects a low fluid level. (Chevrolet)
Ignition switch
Instrument panel
fuse box
Battery
Main
fuse box
Brake fluid
level switch
Anti-lock
brake controller
Proportioning
differential switch
Parking brake switch
(switch is open, parking
brake is released)
Dash warning
light
Warning light fuse
Figure 19-4. Checking one type of parking brake warning light
switch with an ohmmeter. Test with the brake lever in both the
applied and released positions. This will turn the switch on and
off. (Chrysler)
Lever
applied
Switch
terminal
Lever
released
Mounting
bolt
Ohmmeter
Foot-Operated Levers
The foot-operated lever unit should also be checked
for loose fasteners, cracked or broken parts, damaged
ratchet teeth, proper release mechanism function, warning
switch damage or misadjustment, and release operation. If
the parking brake has a vacuum release device, check for
loose or missing hoses and vacuum leaks at the diaphragm.
A vacuum pump and/or vacuum gauge, can be used to
check the vacuum components. Vacuum pumps were dis-
cussed in Chapter 3.
Warning Lights
Warning lights develop one of two problems: they do
not come on or they do not turn off. The following sections
address each problem.
Warning Light Does Not Illuminate
Begin by checking the fuse that controls the warning
light circuit, Figure 19-3. If the warning lightbulb is easily
accessible, make sure the bulb is not burned out. If the
bulb cannot be easily reached, skip this step until you are
sure that the switch and fuse are good.
There are two ways to check warning light switches:
checking the switch itself, or bypassing it. To check the switch,
obtain an ohmmeter. Disconnect the switch connector and
attach the ohmmeter leads between the parking brake switch
terminal and a mounting bolt. If there is continuity (very low
resistance) when the lever is pulled (hand brakes) or depressed
(foot brakes), and there is no continuity when the lever is
returned to the released position, the switch is functioning
properly. A switch being tested with an ohmmeter may be
viewed in Figure 19-4. A self-powered test light can also be
used to make this test.