Temperature Sending Unit (Gm 3000-D) - Toro Groundsmaster 3000 Service Manual

Temperature Sending Unit
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).
Make sure engine is cool and coolant system is
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).
Handle the hot oil with extreme care to prevent
personal injury or fire.
3. Check continuity of the switch component with a
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
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
(GM 3000–D)
CAUTION
CAUTION
SENDING UNIT
TO TEMP GAUGE
(VIOLET WIRE)
TO HIGH TEMP RELAY
(GRAY WIRE)
Rev. A
Page 6 – 22
Figure 36
Figure 37
Figure 38
Groundsmaster 3000/3000–D