ifold valvifold valve. e. The brake coolant prThe brake coolant pressure swessure switchitch
is a normally closed switch that will open atis a normally closed switch that will open at
10 psi. 10 psi. The purpose of this sThe purpose of this switcwitch is to moni-h is to moni-
tor for a low pressure problem in the braketor for a low pressure problem in the brake
cooling cicooling circuit. rcuit. When the presWhen the pressure dropssure drops
below 10 psi, the switch will then close com-below 10 psi, the switch will then close com-
pleting the electrical circuit to the brake faultpleting the electrical circuit to the brake fault
light (Dlight (DS8). S8). It must now be deterIt must now be determined if themined if the
switch (S23) is defective or if a low pressureswitch (S23) is defective or if a low pressure
problem exists in the brake cooling circuit.problem exists in the brake cooling circuit.
There is a pressure test coupling (pressureThere is a pressure test coupling (pressure
check) located on the brake cooling manifoldcheck) located on the brake cooling manifold
at port A. at port A. Plug a pressPlug a pressure gauge inture gauge into the testo the test
port and with the engine running, observe theport and with the engine running, observe the
gauge reading. gauge reading. The maxThe maximum imum pressurepressure
observed should be no more than 600 psi (theobserved should be no more than 600 psi (the
pressure will be between 0 and 600 psi).pressure will be between 0 and 600 psi).
Remember it takes 10 psi to open the switch.Remember it takes 10 psi to open the switch.
If the pressure indicated is above 10 psi, theIf the pressure indicated is above 10 psi, the
brake coolant pressure switch (S23) is defec-brake coolant pressure switch (S23) is defec-
tive and must be replaced.tive and must be replaced.
If all three of the switches, described above, haveIf all three of the switches, described above, have
been provebeen proven to n to be good be good and the brake fault lighand the brake fault light ist is
still illuminated, there is a short on the signal wirestill illuminated, there is a short on the signal wire
#32. #32. Isolate aIsolate and remove nd remove the shortthe short..
Front Wiper CircuitFront Wiper Circuit(Illustration 6-16)(Illustration 6-16).. The front The front
wiper circuit is comprised of a circuit breakerwiper circuit is comprised of a circuit breaker
(CB4), wi(CB4), wiper switcper switch (S7) and wiper motor (B1)h (S7) and wiper motor (B1). . 1212
VDC power is supplied from circuit breaker (CB4)VDC power is supplied from circuit breaker (CB4)
to the B (Battery) posts of the wiper switch (S7).to the B (Battery) posts of the wiper switch (S7).
There are 6 posts on the back of the wiper switchThere are 6 posts on the back of the wiper switch
(S7). (S7). The P (Park) posThe P (Park) post of the wiper swt of the wiper switch isitch is
used for parkiused for parking the wiper motor (ng the wiper motor (B1). B1). When theWhen the
wiper switch is turned off, 12 VDC will be presentwiper switch is turned off, 12 VDC will be present
at the P at the P postpost. . When the wipWhen the wiper swier switch is turntch is turned on,ed on,
12 VDC will be present at the L (Low) or H (High)12 VDC will be present at the L (Low) or H (High)
post of the wiper switch (depending on desiredpost of the wiper switch (depending on desired
speedspeed). ). 12 VDC wil12 VDC will be present at the W (Wal be present at the W (Wash-sh-
er) post of the wiper switch (S7) when the wiperer) post of the wiper switch (S7) when the wiper
switcswitch is depressed. h is depressed. Five wiFive wires are used on theres are used on the
wiper motwiper motor (B1). or (B1). The black wThe black wire of the wiperire of the wiper
motomotor is used for grr is used for ground. ound. The blue wiThe blue wire of there of the
wipwiper motor (Ber motor (B1) is is used for high speed. 1) is is used for high speed. TheThe
yellow wire of the wiper motor (B1) has a constantyellow wire of the wiper motor (B1) has a constant
12 VDC supply to it at all times while the key is at12 VDC supply to it at all times while the key is at
the accessorthe accessory positiy position. on. The red wire of the wThe red wire of the wiperiper
motor (B1) imotor (B1) is used for low ss used for low speed. peed. In this applicIn this applica-a-
tion, 12 VDC will be applied to the red wire whention, 12 VDC will be applied to the red wire when
the wiper swthe wiper switch (S7) iitch (S7) is in the Low positis in the Low position. on. TheThe
green wire of the wiper motor (B1) is used to drivegreen wire of the wiper motor (B1) is used to drive
the wiper motor to the Park position when the wip-the wiper motor to the Park position when the wip-
er switer switch (S7) is turch (S7) is turned off. ned off. There wilThere will be 12 VDCl be 12 VDC
present on the green wire when the wiper switchpresent on the green wire when the wiper switch
(S7) is in the Park position.(S7) is in the Park position.
Top and Rear Wiper CircuitsTop and Rear Wiper Circuits(Illustration 6-16)(Illustration 6-16)..
The top and rear wiper circuits are comprised of aThe top and rear wiper circuits are comprised of a
circuit breakers (CB3 and CB24), wiper switchescircuit breakers (CB3 and CB24), wiper switches
(S8 and S9) and wipe(S8 and S9) and wiper motorr motors (B8 and B9). s (B8 and B9). 1212
VDC power is supplied from circuit breaker (CB3)VDC power is supplied from circuit breaker (CB3)
to the B (Battery) post of the wiper switch (S8)to the B (Battery) post of the wiper switch (S8)
while 12 VDC power is supplied from circuit break-while 12 VDC power is supplied from circuit break-
er (CB24) to the B (Battery) post of the wiperer (CB24) to the B (Battery) post of the wiper
swiswitch (S9tch (S9). ). TherThere are 5 e are 5 postposts on the back of thes on the back of the
wiper swwiper switches (itches (S8 and S9). S8 and S9). The P (Park) posThe P (Park) post oft of
the wiper switches are used for parking the wiperthe wiper switches are used for parking the wiper
motor (B9 and B8). motor (B9 and B8). When the wiper sWhen the wiper switches witches areare
turned off, 12 VDC will be present at the P post.turned off, 12 VDC will be present at the P post.
When the wiper switches are turned on, 12 VDCWhen the wiper switches are turned on, 12 VDC
will be present at the L (Low) post or H (High) postwill be present at the L (Low) post or H (High) post
of the wiper switches, contingent on the speedof the wiper switches, contingent on the speed
selected. selected. 12 VDC wil12 VDC will be present at the W (Wl be present at the W (Wash-ash-
er) post of the wiper switches (S8 or S9) when theer) post of the wiper switches (S8 or S9) when the
wiper swiwiper switch is depressed. tch is depressed. With the wiper swWith the wiper switchitch
(S8 or S9) turned off, 12 VDC is applied at the P(S8 or S9) turned off, 12 VDC is applied at the P
terminal of the wiper motor (B9 or B8) to drive theterminal of the wiper motor (B9 or B8) to drive the
wiper motwiper motor to the Park positor to the Park position. ion. With the wiWith the wiperper
switch (S8 or S9) in the Low position, 12 VDC isswitch (S8 or S9) in the Low position, 12 VDC is
applied to the L terminal of the wiper motor (B9 orapplied to the L terminal of the wiper motor (B9 or
B8) for low speedB8) for low speed. . With the wipWith the wiper switcer switch (S8 orh (S8 or
S9) in the high speed position, 12 VDC is appliedS9) in the high speed position, 12 VDC is applied
to the H terminal of the wiper motor (B9 or B8) forto the H terminal of the wiper motor (B9 or B8) for
high speed. high speed. The wiper mThe wiper motors (B9 and B8) utilotors (B9 and B8) utilizeize
chassis ground.chassis ground.
Defroster Fan MotorsDefroster Fan Motors(B2 and B4, Illustration(B2 and B4, Illustration
6-16)6-16).. The front defroster (B2) and the rearThe front defroster (B2) and the rear
defroster (B4) fan motors are controlled bydefroster (B4) fan motors are controlled by
defroster swdefroster switch (S6). itch (S6). DefrostDefroster switch (S6) iser switch (S6) is
powered by cirpowered by circuit breakcuit breaker (CB9). er (CB9). There is aThere is a
diode between circuit breaker (CB9) and defrosterdiode between circuit breaker (CB9) and defroster
switcswitch (S6). h (S6). Its purpose iIts purpose is to prevent an induceds to prevent an induced
voltage generated by the defroster fan motors (B2voltage generated by the defroster fan motors (B2
and B4), which could prolong engine shut down,and B4), which could prolong engine shut down,
after the ignition switch (S1) is turned to the Offafter the ignition switch (S1) is turned to the Off
position. position. With the defrosWith the defroster switer switch (S6) in the Lowtch (S6) in the Low
position, 12 VDC will be present on wire #40A forposition, 12 VDC will be present on wire #40A for
the front defroster motor (B2) or on wire #40 forthe front defroster motor (B2) or on wire #40 for
the rear defrosthe rear defroster motor (ter motor (B4). B4). With the defrosWith the defrosterter
switch (S6) in the High position, 12 VDC will beswitch (S6) in the High position, 12 VDC will be
present on wire #41A for the front defroster motorpresent on wire #41A for the front defroster motor
(B2) or wire #41 for the rear defroster motor (B4).(B2) or wire #41 for the rear defroster motor (B4).
Both defroster motors (B2 and B4) utilize chassisBoth defroster motors (B2 and B4) utilize chassis
ground.ground.
Heater Fan Heater Fan MotoMotorr(B5, Illustration 6-16)(B5, Illustration 6-16).. TheThe
heater fan motor (B5) is controlled by heaterheater fan motor (B5) is controlled by heater
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