CAUTION:  DO NOT APPLY HEAT ABOVE 375°F (191°C) TO SWITCH PROBE OR THE SWITCH MAY BE DAMAGED.
1)  Check that both MASTER CAUTION lights, the AIR COND annunciator light, and the PACK TRIP OFF light come on at approximately 365 (+ 10)°F (185 (+ 6) °C) and that after lights come on a click is felt at solenoid A of the pack valve.
2)  After click is felt open OVERHEAT circuit breaker, reconnect electrical connector removed in step B.(7)(b), close OVERHEAT circuit breaker and check that mix valve drives to full cold position by observing AIR MIX VALVE position indicator.
(c)  
Depress either MASTER CAUTION light. Check that AIR COND annunciator light and both MASTER CAUTION lights go off, but PACK TRIP OFF light remains on.

(d)  
Depress any system MASTER CAUTION annunciator light. Check that both MASTER CAUTION lights and all master caution annunciator lights come on but, when released, only both MASTER CAUTION lights, AIR COND annunciator light, and PACK TRIP OFF light remain on.

(e)  
Remove heat source.

(f)  
Open OVERHEAT circuit breaker, remove pack valve limit switch connector from pack valve, then close OVERHEAT circuit breaker.

(g)  
Allow sufficient time for compressor discharge overheat switch to cool then push TRIP RESET switch and check that PACK TRIP OFF light, AIR COND annunciator light and both MASTER CAUTION lights go off, and check for click at solenoid A of the pack valve.

(h)  
Install compressor discharge overheat switch in air cycle machine compressor scroll.

(4)  Check turbine inlet overheat switch operation.
(a)  
Move temperature selector knob to MANUAL WARM to drive valve away from full cold position.

(b)  
Remove turbine inlet overheat switch from air cycle machine turbine inlet duct.

(c)  
Apply controlled heat to overheat switch probe while observing MASTER CAUTION light and AIR COND annunciator light on P2 panel and PACK TRIP OFF light on forward overhead panel. 1) Check that both MASTER CAUTION lights, AIR COND annunciator light, and

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PACK TRIP OFF light come on at approximately 210 (+ 10)°F (92 to 104°C). When lights come on check for click at solenoid A of pack valve.
2)  After click is felt, open OVERHEAT circuit breaker, reconnect pack valve limit switch electrical connector removed in step 2.C.(3)(f), close OVERHEAT circuit breaker and check that mix valve drives to full cold position by observing AIR MIX VALVE position indicator.
(d)  
Remove heat source.

(e)  
Open OVERHEAT circuit breaker, remove pack valve limit switch electrical connector from pack valve, then close OVERHEAT circuit breaker.

(f)  
Allow sufficient time for turbine inlet overheat switch to cool, then push TRIP RESET switch and check that PACK TRIP OFF light, AIR COND annunciator light and both MASTER CAUTION lights go off and check for click at solenoid A of pack valve.

(g)  
Install turbine inlet overheat switch in air cycle machine turbine inlet duct.

(h)  
Open OVERHEAT circuit breaker, install pack valve limit switch electrical connector, then close OVERHEAT circuit breaker.

(5)  
Move air conditioning PACK switch to OFF.

(6)  
Close applicable air conditioning equipment bay door.

(7)  
If no longer required, remove electrical power from airplane.

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3.  Pack Protective Circuit Test
A.  General
(1) This procedure makes sure the pack valve closes when an overheat condition occurs.
B.  Equipment and Materials
 (1) Jumper Wire
C.  Prepare for Pack Protective Circuit Test
(1)  
Provide electrical power.

(2)  
Check that all air conditioning circuit breakers are closed (in).

(3)  
Check that the following circuit breakers on circuit breaker panel P6 are closed:

(a)  
MASTER CAUTION (all except FUEL, if installed)

(b)  
INDICATOR LIGHTS, MASTER DIM BUS (9 places)

(c)  
DIM & TEST (1 place)

(4)  
Check warning lights and annunciators.

(a)  
Place LIGHTS switch on lightshield panel (P2-l) to TEST. Check that both MASTER CAUTION lights, the AIR COND annunciator light and PACK TRIP OFF light come on.

(b)  
Move LIGHTS switch to BRT.

(c)  
Press to test PACK TRIP OFF light.
　
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