Taylor THDC-954, Руководство по обслуживанию

Страница: 78 / 100

6-9 6-9 THDC / THDCP - 954 / 955 / 974 (Rev. 06/03) THDC / THDCP - 954 / 955 / 974 (Rev. 06/03)
Single-Pole, Single-Throw, Maintain Contact Single-Pole, Single-Throw, Maintain Contact
Switches.
Switches. A switch is designed with the purpose A switch is designed with the purpose
of controlling an electrical circuit by completing or of controlling an electrical circuit by completing or
opening the circuit
opening the circuit. . With an ohmmeter With an ohmmeter, check the , check the
resistance between the contact points of the resistance between the contact points of the
swit switch. ch. With the swi With the switch closed (com tch closed (completing the pleting the
circuit), the ohmmeter reading should indicate 0 - circuit), the ohmmeter reading should indicate 0 -
40 ohms.
40 ohms. With the swi With the switch open (opening the cir tch open (opening the cir--
cuit), the ohmm cuit), the ohmmeter reading should be infini eter reading should be infinity ty. . If If
the above chec the above checks are good, the swi ks are good, the switch is good. tch is good. If If
any of the above checks fail, the switch is bad and any of the above checks fail, the switch is bad and
must be replaced.
must be replaced.
Single-Pole, Double-Throw, Momentary Rocker Single-Pole, Double-Throw, Momentary Rocker
Switches.
Switches. This type of switch operates on the This type of switch operates on the
principle that the circuit is closed only when the principle that the circuit is closed only when the
swit
switch is held in the clos ch is held in the closed state. ed state. Once the swit Once the switch ch
is released, the ci is released, the circuit wi rcuit will open. ll open. This swi This switch is tch is
checked like an On-Off switch with the exception checked like an On-Off switch with the exception
that the switch must be held closed to complete
that the switch must be held closed to complete
resistance checks.
resistance checks.
Solenoids. Solenoids. A solenoid is an electrical compo- A solenoid is an electrical compo-
nent. nent. When electr When electricity icity is applied to the coi is applied to the coil, the l, the
solenoid wi solenoid will form an el ll form an electromagnet ectromagnet. . The magnet- The magnet-
ic field will pull or push an armature into the coil ic field will pull or push an armature into the coil
(based on appli
(based on application). cation). The armat The armature can be con- ure can be con-
nected to a switch in electrical circuits to turn the nected to a switch in electrical circuits to turn the
swi
switch on or off. tch on or off. An armat An armature can also be used to ure can also be used to
open or close valves. open or close valves.
Solenoids employed as electrical switches can be Solenoids employed as electrical switches can be
troublesh
troubleshot with an ohmmeter ot with an ohmmeter. . Remove the two Remove the two
wires from the two larger posts of the solenoid. wires from the two larger posts of the solenoid.
Energize the solenoi
Energize the solenoid. d. With an ohmmeter With an ohmmeter, check , check
the resis the resistance between the two l tance between the two larger posts. arger posts. The The
ohmmeter should indicate between 0 - 40 ohms ohmmeter should indicate between 0 - 40 ohms
nominally. nominally.
Solenoids employed as hydraulic switches are Solenoids employed as hydraulic switches are
used to open and clos
used to open and close spools of val e spools of valves. ves. The The
simplest way to prove the solenoid coil good is to simplest way to prove the solenoid coil good is to
energize the solenoid and then, with a metal
energize the solenoid and then, with a metal
object, touch the nut that secures the coil to the
object, touch the nut that secures the coil to the
cartri
cartridge. dge. The magnetic f The magnetic field generated when the ield generated when the
coil becomes an electromagnet will be significant coil becomes an electromagnet will be significant
enough to pull the metal object to the nut (some
enough to pull the metal object to the nut (some
solenoids employ a metal nut encased in plastic
solenoids employ a metal nut encased in plastic
and will require removal in order to detect the
and will require removal in order to detect the
magnetic fi
magnetic field). eld). This wil This will prove the coil good; how- l prove the coil good; how-
ever ever, the armature may be stuck , the armature may be stuck. . If the hydraulic If the hydraulic
circuit is still defective at this point, remove the coil circuit is still defective at this point, remove the coil
and cartri
and cartridge. dge. Now energi Now energize the coil, the arm ze the coil, the arma- a-
ture insi ture inside the cartrid de the cartridge should shift. ge should shift. If the arma- If the arma-
ture inside the cartridge did not shift and the coil is ture inside the cartridge did not shift and the coil is
magnetize
magnetized, d, replace the replace the cartri cartridge. dge.
Exercise care not to reverse polarity because Exercise care not to reverse polarity because
some solenoids employ internal diodes which can
some solenoids employ internal diodes which can
be destroyed when the pol
be destroyed when the polarity is r arity is reversed. eversed. The The
solenoids employed on the transmission control solenoids employed on the transmission control
valve contai
valve contain diodes. n diodes. The black wi The black wire of the coil re of the coil
connects to the ground side of the circuit while the connects to the ground side of the circuit while the
red wire goes to the positive side of the circuit. red wire goes to the positive side of the circuit.
Diodes Diodes (Illustration 6-10) (Illustration 6-10) .. Diodes are one-way Diodes are one-way
conductor conductors that provide isolat s that provide isolation. ion. Current flo Current flow w
thr through a diode is fro ough a diode is from anode to catho m anode to cathode. de. They They
are easily proven good by using an ohmmeter. are easily proven good by using an ohmmeter.
When using the ohmmeter, place the leads of the
When using the ohmmeter, place the leads of the
ohmmeter on the opposite ends of the diode.
ohmmeter on the opposite ends of the diode.
Observe the ohmm
Observe the ohmmeter reading. eter reading. Then revers Then reverse the e the
ohmmeter leads on the ends of the diode. ohmmeter leads on the ends of the diode.
Observe t
Observe the ohmmeter he ohmmeter reading. reading. The ohmmet The ohmmeter er
readings should indicate a higher ohm resistance readings should indicate a higher ohm resistance
in one direction opposed to the other direction
in one direction opposed to the other direction
because the current generated by the ohmmeter
because the current generated by the ohmmeter
is sufficient enough to forward-bias the diode.
is sufficient enough to forward-bias the diode.
C Ca atth ho od de e A An no od de e
Curren Current t Flow Flow
Illust Illustration ration 6-10. 6-10. Diode Diode
https://www.forkliftpdfmanuals.com/