15.
Overtemperature Switch (fig. 1-39).
The system has the overtemperature switch located in the bleed air
outlet duct just upstream of the conditioned air temperature sensor.
This switch has a three-pin electrical connector and a probe
partially filled with a volatile liquid.
Operation.
The
overtemperature
switch
detects
an
overtemperature condition in the conditioned air duct. The
switch turns on the SPONSON OUT OVER HEAT warning light on
the commander's control panel if the temperature switch
detects a temperature above 152,F ƒ7,F. This switch works
on pressure created in the liquid filled probe.
The
pressure created in the probe is directly proportional to
the temperature it senses.
If the temperature reaches the control point (152,F ƒ7,F),
the pressure moves a stainless steel diaphragm to actuate
the switch and close the contacts.
The contacts of the
switch remain closed until the temperature drops to 130,F
ƒ5,F, which is the reset point.
Failure Mode.
If the switch contacts stick closed on
contact "B," the light stays on, and if the switch contacts
stick closed on contact "C," the light will not light.
Figure 1-39.
Overtemperature Switch Location.
34
OD1705
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