ARMY TM 9-6115-604-12
NAVY NAVFAC P-8-633-12
MAINTENANCE OF COOLANT TEMPERATURE SWITCHES WT1/WT2 . The coolant temperature switch WT2
(see Figure 3-3) senses engine coolant temperature. When coolant exceeds 208 ± 2°F (98 ± 1°C), contacts 8
and C close. When coolant exceeds 217 ± 2 F (103 ± 1° C), contacts A and D close. The first condition
activates a warning alarm; the second condition results in automatic shutdown of the engine.
Using a drain or sump, drain the radiator in accordance with paragraph 3-12.
Disconnect electrical connector from switch. Remove switch.
Test. See Figure 4-27.
Connect multimeter set to RX1 scale across switch contacts A and D.
Suspend switch in a container of antifreeze. Switch should be inserted so that sensing element is
completely immersed but connector end is out of antifreeze.
Heat antifreeze gradually and stir so that heat is evenly distributed.
Check temperature of antifreeze with a reliable thermometer.
When antifreeze has reached 217°F (103 C), the switch should close and the multimeter should
read less than 1 ohm.
Allow antifreeze to cool. As the temperature drops the switch should open and the multimeter should
read infinite ohms.
Repeat steps (1) through (6), above, for contacts B and C. The switch should activate at 208°F
The switch is not repairable if It does not operate within the above limits it must be replaced.
Install switch (see Figure 3-3) Torque to maximum 15 pound-feet (20 newton-meters). Connect
Refill radiator in accordance with paragraph 3-12.
MAINTENANCE OF COOLANT LEVEL SWITCHES S13 AND S14 . Coolant level switches S13 and S14 (see
Figure 3-3) are immersion sensitive switches. When above the radiator water line, the normally open contacts close.
Actuation of switch S13 results in a warning alarm. Actuation of switch S14 results in automatic shutdown of the engine
Figure 4-27. Test of Coolant Temperature Switch