737 MAX Flight Crew Operations Manual
Supplementary Procedures -
Anti–Ice, Rain
SP.3.4
MN-FLT-OH-201
Window Heat System Tests
Overheat Test
The overheat test simulates an overheat condition to check the overheat
warning function of the window heat system.
WINDOW HEAT switches ................................................................ ON
WINDOW HEAT TEST switch .................................................... OVHT
OVERHEAT lights – On
YA201 - YD256, YF631 - YL956, YN107 - YV671
ON lights – Extinguish
Lights extinguish after approximately 1 minute.
MASTER CAUTION – On
ANTI–ICE system annunciator – On
WINDOW HEAT switches ............................................................. Reset
Position the WINDOW HEAT switches OFF, then ON.
Power Test
YA201 - YD256, YF631 - YL956, YN107 - YV671
The power test verifies operation of the window heat system. The test may
be accomplished when any of the window heat ON lights are extinguished
and the associated WINDOW HEAT switch is ON.
WINDOW HEAT switches ................................................................ ON
Note:
Do not perform the power test when all ON lights are
illuminated
WINDOW HEAT TEST switch ...................................................... PWR
The controller is forced to full power, bypassing normal temperature
control. Overheat protection is still available.
WINDOW HEAT ON lights ..................................................Illuminated
If any ON light remains extinguished, the window heat system is
inoperative. Observe the maximum airspeed limit of 250 kts below
10,000 feet.
March 1, 2021
