b) Move PACK switch to ON (OPEN).
c) Check that mix valve remains in the full cold position.
d) Move the selector knob to manual warm and check that mix valve drives

toward HOT. e) Move the selector knob back to the automatic range at a setting below cabin temperature. f) Check that the mix valve moves to the full COLD position.
(c)  
Check that air is entering the cabin by feel at cabin inlet.

(d)  
Move AIR TEMP selector to SUPPLY DUCT position.

(e)  
Move and hold temperature selector to manual WARM while observing temperature indicator and check that duct temperature begins to rise.

(f)  
Move and hold temperature selector to manual COOL while observing temperature indicator and check that duct temperature begins to drop.

(g)  
Move and hold temperature selector to manual WARM while observing temperature indicator and after duct temperature has reached approximately 100°F (38°C), move selector to AUTO COOL.

(h)  
After allowing time for temperature to stabilize, check that indicator reads 39 +5°F (4 +3°C).

NOTE:  If temperature indicated is not within the above limits and/or exhibits signs of surging, there is apparently a problem in the engine bleed air compression control system (21-11-0) or the water separator 35°F control system (21-51-0).

(i)  
Move PACK switch to OFF (CLOSE)

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(4)  
Test Duct Temperature Limit Sensor (Topping Control)

(a) 
 General

1)  In order to perform the topping control test it is necessary to start with a cabin temperature of 75°F (24°C) or less.

(b)  
Move AIR TEMP selector to PASS CABIN (CABIN) position and check that
temperature is 75°F (24°C) or less.

(c)  
If temperature is above 75°F (24°C), perform the following; if not move PACK switch to ON (OPEN) and proceed to (d). 1) Move PACK switch (es) to ON (OPEN). 2) Move temperature selector(s) to COOL and leave until passenger cabin

temperature drops below 75°F (24°C). 3) If both packs were used to lower cabin temperature move PACK switch for system not being tested to OFF (CLOSE).

(d)  
Move AIR TEMP selector to SUPPLY DUCT position.

(e)  
Push-to-test DUCT OVERHEAT and PACK TRIP OFF lights.

(f)  
Move temperature selector to AUTO full WARM position and check that duct temperature increases to 140 +20°F (60 +11°C) and that DUCT OVERHEAT and/or PACK TRIP OFF lights do not come on.

(g)  
Move PACK switch to OFF (CLOSE).

(5)  
Test Duct Overheat Protection Operation

(a)  
Check that AIR TEMP selector is in SUPPLY DUCT position.

(b)  
Move PACK switch to ON (OPEN).

(c)  
Move temperature selector to MANUAL OFF.

(d)  
Gradually drive mix valve toward hot by intermittently moving temperature selector to MANUAL WARM while observing temperature indicator, AIR MIX VALVE position indicator, DUCT OVERHEAT light, PACK TRIP OFF light and MASTER CAUTION lights.

(e)  
Check that when the following conditions occur, the temperature indicator reads above 170°F (76.5°C).

NOTE:  If duct temperature is increased too fast the duct overheat switch may trip at a temperature below 170°F (76.5°C).
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NOTE:  Indicator may read anywhere between 170°F and above to off-scale because of the temperature indicating system tolerance and time lag as well as the anticipating behavior of the thermal switch.
1)  DUCT OVERHEAT light and MASTER CAUTION lights come on.
NOTE:  OVERHEAT light for system not being tested might also come on since both thermal switches will feel main distribution manifold air temperature.
2) PACK TRIP OFF light remains out.
3) AIR MIX VALVE drives to full COLD after the warning lights come on.

(f)  
Allow time for duct temperature to drop below 170°F (76.5°C) then push the TRIP RESET switch and check that warning lights go out.

(g)  
Move temp selector to MANUAL WARM and check that mix valve drives toward HOT.

(h)  
Move PACK switch to OFF (CLOSE).

(6)  Restore Airplane to Normal Configuration
(a)  
　
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