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TRUCK SERVICE MANUAL
TM 5-4210-230-14&P-1
INSTRUMENTS
Fig.  20 Water Temperature Gauge Circuit Diagram
temperature   coefficient.      The   decrease   in   sender   resistance
increases   the   current   flowing   in   the   "hot"   coil,   reaching   a
maximum at the full-scale temperature.  With maximum current
in  the  "hot"  coil,  the  pointer  and  armature  assembly  will  align
itself  with  the  resultant  magnetic  field  produced  by  the  three
coils  at  the  full-scale  position.    Thus,  the  interaction  of  the
magnetic fields of the three coils produces a resultant magnetic
field  which  controls  the  rotation  and  position  of  the  armature
and pointer assembly.
IMPORTANT
The  gauge  is  grounded  to  chassis  through  the
ground 
terminal 
when 
plugged 
into 
the
instrument cluster printed circuit.
The  sender  terminal  is  the  first  terminal  clockwise  from
ground  terminal  (when  viewed  from  back  side).    The  ignition
terminal is directly opposite from sender terminal.
Check for faulty components as follows:
1.
Disconnect sender wire at sender (Fig.  20).
2.
Connect one lead of SE-2781 Gauge Tester to sender
wire and the other lead to a good ground.
3.
Set the gauge tester for 55 ohms (left knob at "50" and
right  knob  at  "5").    Turn  key  switch  on  and.    gauge
should  read  at  full  scale.    (Pointer  within  2  pointer
widths of hash mark).
4.
Set  gauge  tester  for  113  ohms  (left  knob  at  100  and
right  knob  at  13  ohms).    Gauge  should  read  at  half
scale.  (Pointer within 2 pointer widths of hash mark).
5.
Set gauge tester for 1365 ohms (center knob at "1365"
and other knobs at "O").  The gauge should now read
at  low  scale.    (Pointer  within  2  pointer  widths  of  hash
mark).
If results of Steps 3 thru 5 are satisfactory gauge is OK
and sender must be replaced.
CTS-2735R  Page 12
PRINTED IN UNITED STATES OF AMERICA
 
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