the bleed air temperature becomes too hot, and if the bleed
air passages become clogged, the bleed air flow and the
final distribution air flow decrease.
The overtemperature switch, located
in the bleed air outlet duct,
just downstream from the precooler,
senses the temperature of the
bleed air just after it leaves the
This switch has a
filled with liquid and a three-
pin electrical connector.
Overtemperature Switch Location.
Operation (fig. 1-11).
an overtemperature condition at the precooler bleed air
When the switch detects an overtemperature
condition (above 325,F ƒ10,F), it turns on the (SPONSON IN
OVER HEAT) warning light on the commander's control panel.
The switch works on pressure created in the liquid filled
The pressure created in the probe is directly
proportional to the temperature of the bleed air.
If the temperature reaches the control point (325,F
ƒ10,F), the pressure created in the probe moves a stainless
steel diaphragm to actuate the switch and close the
The contacts of the switch remain closed until
the temperature of the bleed air drops to 300,F ƒ15,F, the