(e)  
Make sure that the EICAS advisory message HEAT P/S CAPT does not show.

 (f)  
Make sure that the upper left pitot probe head temperature increases.

 (g)  
Close 7F23, LANDING GEAR DSP & CONT ALTN circuit breaker on the P7, Overhead Circuit Breaker Panel.

 (h)  
Open 6D34, PROBE HEAT IND L and 6D30, PROBE HEAT PITOT L circuit breakers on the P6, Main Power Distribution Panel.

 (i)  
Install relay, R7433, in the P414, Left Power Distribution Center.

 S 715-023
 (3)  Make sure that the upper left pitot probe strut heater operates:
 (a)  
Remove relay, R7431, from the P414, Left Power Distribution Center.

 (b)  
Close 6D34, PROBE HEAT IND L and 6D30, PROBE HEAT PITOT L circuit breakers on the P6, Main Power Distribution Panel.

 (c)  
Open 7F23, LANDING GEAR DSP & CONT ALTN circuit breaker on the P7, Overhead Circuit Breaker Panel.

 (d)  
Make sure that the EICAS advisory message HEAT P/S CAPT does not show.

 (e)  
Make sure that the upper left pitot probe strut temperature increases.

 (f)  
Close 7F23, LANDING GEAR DSP & CONT ALTN circuit breaker on the P7, Overhead Circuit Breaker Panel.

 (g)  
Open 6D34, PROBE HEAT IND L and 6D30, PROBE HEAT PITOT L circuit breakers on the P6, Main Power Distribution Panel.

 (h)  
Install relay, R7431, in the P414, Left Power Distribution Center.

 S 715-024
 (4)  Make sure that the upper left pitot probe heater operates on the ground with an engine on signal:
 (a)  
Remove relay, R7433, from the P414 Left Power Distribution Center.

 (b)  
Close 6D34, PROBE HEAT IND L and 6D30, PROBE HEAT PITOT L circuit breakers on the P6, Main Power Distribution Panel.

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BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
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747-400 MAINTENANCE MANUAL
 (c)  
Set the S1 switch on the YMLA001 ENG 1 N2 speed card in the forward electrical systems card file to TEST.

 (d)  
Make sure that the EICAS advisory message HEAT P/S CAPT does not show.

 (e)  
Make sure that the upper left pitot probe head temperature increases at a lower rate.

 (f)  
Set the S1 switch on the YMLA001 ENG 1 N2 speed card to NORMAL.

 (g)  
Alternative steps to do a check of the probe heater operation: 1) Set the S1 switch on the YMLA001 ENG 1 N2 speed card to

 TEST. 2) Measure the voltage at Pin B1 of Relay socket DR7431. 3) Make sure the voltage measurement is from 60 to 65 volts,
 with a digital multimeter on the AC scale. 4) Set the S1 switch on the YMLA001 ENG 1 N2 speed card to NORMAL.
 (h)  
Open 6D34, PROBE HEAT IND L and 6D30, PROBE HEAT PITOT L circuit breakers on the P6, Main Power Distribution Panel.

 (i)  
Install relay, R7433, in P414 Left Power Distribution Center.

 G. Lower Left Pitot Probe System Test
 S 865-025
 (1)  
Close 6D34, PROBE HEAT IND L and 6D32, PROBE HEAT AUX PITOT L circuit breakers on the P6, Main Power Distribution Panel.

 S 715-026

 (2)  
Make sure that the lower left pitot probe heaters operate:

 (a)  
Make sure that the EICAS advisory message HEAT P/S L AUX shows.

 (b)  
Make sure that the lower left pitot probe temperature does not increase.

 (c)  
Open 7F23, LANDING GEAR DSP & CONT ALTN circuit breaker on the P7, Overhead Circuit Breaker Panel.

 (d)  
Make sure that the EICAS advisory message HEAT P/S L AUX does not show.

 (e)  
Make sure that the lower left pitot probe temperature increases.

 (f)  
Close 7F23, LANDING GEAR DISP & CONT ALTN circuit breaker on the P7, Overhead Circuit Breaker Panel.

 (g)  
Make sure that the EICAS advisory message HEAT P/S L AUX shows.

 S 715-027
 (3) Make sure that the lower left pitot probe head heater operates:
 (a)  
Open 6D34, PROBE HEAT IND L and 6D32, PROBE HEAT AUX PITOT L circuit breakers on the P6, Main Power Distribution Panel.

 (b)  
　
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