Thermo King T-1080S, Maintenance Manual

Page: 100 / 191

Engine Maintenance
99
5. Refill the expansion tank with coolant.
6. Connect the wire harness connector to the
coolant level switch.
Coolant Level Switch for Units with
Coolant Expansion Tank and
Overflow Bottle (Starting 10/16)
The coolant expansion tank uses a reed type
coolant level switch. The coolant level switch
senses the position of the magnetic float inside the
expansion tank. When the coolant level is above
the switch, the float is in the upper position and
the switch is closed. When the coolant level is
below the switch, the float is in the lower position
and the switch is open.
Testing the Coolant Level Switch
Testing the switch in the unit is accomplished by
adjusting the coolant level and also by removing
the expansion tank from the unit by flipping the
tank upside down and right side up.
1. Remove the wire harness connector from the
coolant level switch.
2. Use an ohmmeter to check the continuity of
the switch at the connection pins.
3. Make sure the coolant level is above the
switch and check the continuity of the switch.
The switch should be closed. If you removed
the tank from the unit, do this check with the
tank upside down.
4. Drain coolant from the expansion tank until
the coolant level is well below the switch level
and check continuity of the switch. The switch
should be open. If you removed the tank from
the unit, do this check with the tank right side
up.
5. Replace the switch if it is does not close in
step 3 and does not open in step 4.
Checking the Float
The float is made of polypropylene foam. It is
unlikely that the float would fail unless it sticks
inside the tank so it cannot move.
1. Make sure the coolant level is above the float.
2. Slowly drain coolant from the expansion tank
and watch the float. The float should drop
with the coolant level.
3. If the float did not drop with the coolant level,
remove the expansion tank from the unit.
4. Flip the expansion tank upside down and right
side up to see if the float moves inside the
expansion tank. Replace the expansion tank
with a new one if the float is stuck or does not
move with the coolant level.
Replacing the Coolant Level Switch
1. Disconnect the wire harness connector from
the coolant level switch.
2. Turn the coolant level switch 1/4 turn to
loosen it and remove it from the tank.
1. Orientation Mark Down
Figure 180: Coolant Level Switch
1. Coolant Level Switch
2. O-Ring
3. Coolant Expansion Tank
Figure 181: Coolant Level Switch Components
1
ARA2510
1
2
3