196 CHAPTER NINE
~
~
lI:
~:"-
Oil
pres
sure
::; sender
Waming
lamp
Cootant
temperature
sender
Fu
~
K.y
Swit
ch
1
: Banery
pressure sender on 2GM, 2GM20. JGM, 3GM30, 3HM
and J HM35 engines is located below the oil filler as
shown in Figul"e 24.
To check the oil pressure sender, proceed as follows:
CAUTION
Before checking the
oil
pressure sender,
make sure the engine isfilled with oil.
I. Disconnect the wire at the sender terminal.
2. Connect an ohmmeter between the sender terminal and
the hex on the base
of
the sender.
3. With the engine
off
the meter should show continuity.
4. Start the engine. As the oil pressure builds above 9.R
kPa (1.4 psi), the meter should switch from continui ty to
no continuity.
If
it docs not, replace the sender unit.
Coolant T
emp
er
a
tur
e Send er
Refer 10 the coolant temperature circuit in Fi
gur
e 25,
The sender is open at
ambient temperature, which pre-
vents current from lighting the warning lamp and activat-
ing the alarm buzzer. Whcn coo lant rises above the
specification. the sender closes,
the warning lamp and the
alarm buzzer come on.
On IGM and IGM 10 engines, the coolant temperature
sensor is located on the cylinder head (f igure 26). The
coolant temperature sensor on two or three cyl inder en-
gines is located on the front or side
of
the thermostat hous-
ing
(Fig
ur
e 27
,t
ypical).
Two different senders may
be used depending on the
type
of
cooling system. Engines equipped with seawater
cooling are equipped with a sender that is color-coded
white and has a closed temperature
of
148-154° F (63-67°
C). Engines equipped with freshwater cooling arc
equipped with a sender that is color-coded green and has
a
closed temperature
of
193-202° F (89_95° C).
To check the coolant sender, proceed as follows:
I. Remove the switch from the engine.
2. Connect a digital ohmmeter to the switch.
3. Immerse the sending unit and a cooki ng thermometer
in a container
of
oil.
4. Heat the container over a flamclcss heat source and
note the ohmmeter reading. The switch should close as
follows:
a. seawater switch
(white)-148-154
° F (63-67 ° C).
b. freshwaterswitch (g
recn}--
193-202
Q
F (89-95°C).
5. Remove the container from the heat and let itcool. The
switch should reopen as follows:
a. seawater switch (white}--136° F (58°
C).
b. freshwater switch (g
reen}--
I90° F (88° C).
6. Replace the switch if'it does not function as specified
at each temperature range.
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