Engine Maintenance
101
Coolant Level Switch
The plastic 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.
NOTE: Figure 163 shows the expansion tank in
two pieces. The two pieces are bonded together
when the tank is assembled, so it cannot be
disassembled, but the coolant level switch can be
replaced.
Testing the Coolant Level Switch
You can test the switch in the unit by adjusting the
coolant level. You can also remove the expansion
tank from the unit and test the switch by flipping
the expansion 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.
3. Place the new coolant level switch in the tank.
Align the tabs on the switch with the slots in
the tank and turn the switch 1/4 turn to tighten
it.
1.
Float
2.
Coolant Level Switch
Figure 163: Plastic Expansion Tank
ARA1911
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