Taylor THDC-954, Руководство по обслуживанию

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6-13 6-13 THDC / THDCP - 954 / 955 / 974 (Rev. 06/03) THDC / THDCP - 954 / 955 / 974 (Rev. 06/03)
Electrical System Troubleshooting Electrical System Troubleshooting
Some of the components described in this section Some of the components described in this section
are optional equipment.
are optional equipment.
Eng Oil light Eng Oil light (DS1, (DS1, Illust Illustration 6-16) ration 6-16) .. The engine The engine
oil light will illuminate when engine oil pressure oil light will illuminate when engine oil pressure
swit switch (S17, Illustr ch (S17, Illustration 1-6) has closed. ation 1-6) has closed. The The
engine oil pressure switch will close between 7 - engine oil pressure switch will close between 7 -
10 psi on falling engine oil pressure.
10 psi on falling engine oil pressure.
Battery light Battery light (DS3, Illustration 6-16) (DS3, Illustration 6-16) .. When the When the
battery light illuminates, it lets the operator know battery light illuminates, it lets the operator know
that there is a problem wit
that there is a problem with the alternator h the alternator. . Refer Refer
to the to the Component Troubleshooting Component Troubleshooting of the of the Alter- Alter-
nator nator found earlier in this section. found earlier in this section.
Seat Belt light Seat Belt light (DS4, Illustration 6-16) (DS4, Illustration 6-16) .. The seat The seat
belt light (DS4) will only illuminate when the key is belt light (DS4) will only illuminate when the key is
in the ignition position and the seat belt is unfas-
in the ignition position and the seat belt is unfas-
tened.
tened. With the s With the seat belt fas eat belt fastened, the seat bel tened, the seat beltt
switch (S18) will send a ground through wire #38, switch (S18) will send a ground through wire #38,
energizing the seat belt relay (K2) and breaking
energizing the seat belt relay (K2) and breaking
the contact between pins #30 and #87A of relay
the contact between pins #30 and #87A of relay
(K2), removing the ground from the seat belt light
(K2), removing the ground from the seat belt light
(DS4).
(DS4).
Shift Fail light Shift Fail light (DS6, Illustration 6-16, if equipped (DS6, Illustration 6-16, if equipped
with APC 70) with APC 70)
..
The shift fail light (DS6) is con- The shift fail light (DS6) is con-
trolled by the APC 70 and will illuminate only when trolled by the APC 70 and will illuminate only when
the operator has attempted an improper shifting
the operator has attempted an improper shifting
procedure.
procedure. The only purpose of thi The only purpose of this light is t s light is to let o let
the operator know that he or she is outside of the the operator know that he or she is outside of the
operating
operating parameter parameters. s.
Low Air light Low Air light (DS7, (DS7, Illust Illustration 6-16) ration 6-16) .. The low air The low air
light (DS7) will illuminate when the air pressure light (DS7) will illuminate when the air pressure
falls below 75 psi.
falls below 75 psi. The low air pressur The low air pressure switch e switch
(S13), a normally closed switch, will close when (S13), a normally closed switch, will close when
the air pressure drops below 75 psi, sending
the air pressure drops below 75 psi, sending
ground through wire #31 (Illustration 6-16) com- ground through wire #31 (Illustration 6-16) com-
pleting the ci
pleting the circuit to the low rcuit to the low air light ( air light (DS7). DS7). In In
addition to the low air light being illuminated, an addition to the low air light being illuminated, an
audible alarm will be heard from the low air / shut
audible alarm will be heard from the low air / shut
down buzzer
down buzzer (LS5). (LS5). When the air When the air pressur pressure drops e drops
to 60 psi, the parking brake valve will pop out, to 60 psi, the parking brake valve will pop out,
applying the parking brake, closing the parking
applying the parking brake, closing the parking
brake switc
brake switch (S11). h (S11). As a result, this will energiz As a result, this will energize e
the brake saver relays (K23 and K31, Illustration the brake saver relays (K23 and K31, Illustration
9C-2), taking away the 12 VDC signal from the
9C-2), taking away the 12 VDC signal from the
forward and reverse solenoids of the control valve
forward and reverse solenoids of the control valve
that is located on the transmi
that is located on the transmission. ssion. This inhibi This inhibits ts
the operator fro the operator from drivi m driving through the brakes. ng through the brakes. The The
air pressure gauge in the instrument panel will air pressure gauge in the instrument panel will
assist in determining if the low air switch (S13) is assist in determining if the low air switch (S13) is
defective, if a short exists on wire #31, or if a low defective, if a short exists on wire #31, or if a low
air pressur
air pressure problem exists e problem exists. . If the air pressure If the air pressure
gauge indicates above 75 psi, remove wire #31 gauge indicates above 75 psi, remove wire #31
from the low ai
from the low air pressur r pressure switc e switch (S13). h (S13). If the low If the low
air light (DS7) does not go out, wire #31 is shorted air light (DS7) does not go out, wire #31 is shorted
out.
out.
Brake Fault light Brake Fault light (DS8, Illustration 6-16) (if (DS8, Illustration 6-16) (if
equipped) equipped) .. There are three signals in parallel There are three signals in parallel
capable of illuminating the brake fault light (DS8). capable of illuminating the brake fault light (DS8).
It is imperative that the technician understand how It is imperative that the technician understand how
these switches work to isolate the source of the
these switches work to isolate the source of the
failure.
failure. The simpl The simplest way to tr est way to troubleshoot is to oubleshoot is to
remove the signal wire #32 from the switches remove the signal wire #32 from the switches
(S23
(S23, S24, and S27), one switc , S24, and S27), one switch at h at a time. a time. Star Startt
the engine and see if the brake fault light (DS8) is the engine and see if the brake fault light (DS8) is
illum
illuminated. inated. By removi By removing the signal wir ng the signal wire #32 from e #32 from
the switch (S23, S24, or S27), the switch will be the switch (S23, S24, or S27), the switch will be
elimi
eliminated from the circ nated from the circuit. uit. Once the defective Once the defective
circuit has been removed, the brake fault light circuit has been removed, the brake fault light
(DS8) wi
(DS8) will not illumi ll not illuminate. nate. Next, the techni Next, the technician cian
must determine if the switch is bad or if the circuit, must determine if the switch is bad or if the circuit,
the switch (S23, S24, or S27) is monitoring, is at
the switch (S23, S24, or S27) is monitoring, is at
fault.
fault.
Troubleshoot the switches (S23, S24, and S27) as Troubleshoot the switches (S23, S24, and S27) as
follows:
follows:
1. 1. The power The power cluster cluster overstr overstroke indi oke indicator s cator switch witch
(S27) is located on the end cover between the (S27) is located on the end cover between the
shell assembly and the tube cylinder of the
shell assembly and the tube cylinder of the
power cluster
power cluster. . The overstrok The overstroke indicator swit e indicator switch ch
is a normall is a normally open switc y open switch. h. A visual ins A visual inspection pection
of the switch will confirm overstroke condition. of the switch will confirm overstroke condition.
The brass colored indicator rod will be protrud-
The brass colored indicator rod will be protrud-
ing from the end cover approximately 3/4” to
ing from the end cover approximately 3/4” to
1”.
1”. The indicato The indicator rod must be phys r rod must be physically ically
reseated. reseated. The most The most common c common cause of the ause of the
brake fault light (DS8) illuminating is when an brake fault light (DS8) illuminating is when an
overstr
overstroke condition oke condition has has occurr occurred. ed.
2. 2. The brak The brake coolant e coolant temperatur temperature swi e switch ( tch (S24, S24,
Illustration 6-16) is located in the brake cooling Illustration 6-16) is located in the brake cooling
valve.
valve. The brake coolant t The brake coolant temperature s emperature switch witch
is a normally open switch that will close at is a normally open switch that will close at
190
190 _ _ F F. . The simplest way to check this sw The simplest way to check this switch itch
is to turn the truck off and allow the truck to is to turn the truck off and allow the truck to
cool.
cool. With an ohmmeter With an ohmmeter, measure the resis , measure the resist- t-
ance between the posts on the switch and the ance between the posts on the switch and the
chassis
chassis ground. ground. The ohmmet The ohmmeter reading er reading
should indicat should indicate infinity (open cir e infinity (open circuit). cuit). If the If the
ohmmeter reading indicates a short, then the ohmmeter reading indicates a short, then the
brake coolant temperature switch (S24) must
brake coolant temperature switch (S24) must
be replaced.
be replaced. Care mus Care must be taken to i t be taken to insure nsure
that a good chassis ground is obtained. that a good chassis ground is obtained.
3. 3. The brak The brake coolant e coolant pressure pressure swit switch (S23, ch (S23,
Illustration 6-16) is located in the brake man- Illustration 6-16) is located in the brake man-
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