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Temperature Sending Unit (GM 3000–D)
The temperature sending unit is located on the top right
side of the water outlet box, which is located on the front
end of the engine block. It has a blue connector with gray
and violet wires. The violet wire supplies a signal to the
high coolant temperature relay from the switch compo-
nent of the sending unit. The gray wire supplies a signal
to the temperature gauge from the thermistor compo-
nent of the sending unit (Fig. 36).
Figure 36
CAUTION
depressurized before removing the temperature
sending unit.
1. Lower the coolant level in the engine and remove
the temperature sending unit from the engine.
2. Put the switch in a container of oil with a thermome-
ter and slowly heat the oil (Fig. 38).
CAUTION
Handle the hot oil with extreme care to prevent
personal injury or fire.
SENDING UNIT
Make sure engine is cool and coolant system is
TO TEMP GAUGE
(VIOLET WIRE)
TO HIGH TEMP RELAY
(GRAY WIRE)
3. Check continuity of the switch component with a
Figure 37
multimeter (ohms setting). Check continuity between
post 2 and the sender casing. The switch is normally
open and should close between 226 to 234_F (108 to
112_C) (Fig. 37).
4. Allow the oil to cool. The switch should open below
226_F (108_C).
5. After oil has cooled below 158_F (70_C), slowly
heat oil and switch again (Fig. 38).
6. Check resistance of the thermistor component with
Figure 38
a multimeter. Check resistance between post 1 and the
sender casing (Fig. 37).
A. The resistance should be about 390 ohms at
158_F (70_C).
B. As the temperature increases,the resistance
should be about 143 ohms at 212_F (100_C).
Electrical System
Page 6 – 22
Rev. A
Groundsmaster 3000/3000–D