Engine Temperature Sender - Toro Reelmaster 3550-D Service Manual

Engine Temperature Sender

The engine temperature sender is located above the al-
ternator, in the thermostat housing (Fig. 43). The resist-
ance of the temperature sender reduces as the engine
coolant temperature increases.
The TEC controller uses input from the temperature
sender to control the high temperature warning light on
the operator's control panel (on or off). Using inputs from
the temperature sender and other switches in the inter-
lock system, the TEC controller controls the energizing
of the engine start relay, the fuel stop solenoid and fuel
pump, and the proportional relief valve (PRV) used to
drive the cutting unit motors (see Table 3: Input Condi-
tions Required to Illuminate Diagnostic Display Outputs
in this chapter).
Testing
1. Park machine on a level surface, lower cutting units,
stop engine, engage parking brake and remove key
from the ignition switch.
2. Locate temperature sender on engine and discon-
nect wire harness connector from sender.
CAUTION
Make sure engine is cool before removing the
temperature sender from engine.
3. Lower coolant level in the engine and remove the
temperature sender from the thermostat housing.
4. Put sender in a container of oil with a thermometer
and slowly heat the oil (Fig. 44).
CAUTION
Handle the hot oil with extreme care to prevent
personal injury or fire.
NOTE: Prior to taking resistance readings with a digital
multi meter, short the meter test leads together. The me-
ter will display a small resistance value (usually 0.5
ohms or less) due to the internal resistance of the meter
and test leads. Subtract this value from from the mea-
sured value of the component you are testing.
Electrical System
1. Engine temp. sender
2. Alternator
5. Check resistance of the sender with a multimeter
(ohms setting) as the oil temperature increases.
A. The meter should indicate from 11.4 to 13.6
k−ohms at 68F (20C).
B. The meter should indicate from 2.3 to 2.6 k−ohms
at 140F (60C).
C. The meter should indicate from 640 to 720 ohms
at 212F (100C).
6. Replace temperature sender if necessary.
7. Install temperature sender:
A. Clean threads of water flange and temperature
sender thoroughly. Apply thread sealant to the
threads of the sender.
B. Screw sender into the water flange until it is finger
tight. Then, tighten sender an additional 2 to 3 full
turns.
C. Connect wire harness connector to sender.
8. Fill engine cooling system.
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Figure 43
3. Oil pressure switch
Figure 44
Reelmaster 3550−D/3555−D/3575−D