(c)  
Open 7H8, GND SAFETY RELAY circuit breaker on the P7, Overhead Circuit Breaker Panel.

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

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

 (f)  
Close 7H8, GND SAFETY RELAY circuit breaker on the P7, Overhead Circuit Breaker Panel.

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

 S 715-032
 (3) Make sure that the upper right pitot probe head heater operates:
 (a)  Open 6D35, PROBE HEAT IND R and 6D31, PROBE HEAT PITOT R circuit breakers on the P6, Main Power Distribution Panel.
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 (b)  
Remove relay, R7434, from the P415, Right Power Distribution Center.

 (c)  
Close 6D35, PROBE HEAT IND R and 6D31, PROBE HEAT PITOT R circuit breakers on the P6, Main Power Distribution Panel.

 (d)  
Open 7H8, GND SAFETY RELAY circuit breaker on the P7, Overhead Circuit Breaker Panel.

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

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

 (g)  
Close 7H8, GND SAFETY RELAY circuit breaker on the P7, Overhead Circuit Breaker Panel.

 (h)  
Open 6D35, PROBE HEAT IND R and 6D31, PROBE HEAT PITOT R circuit breakers on the P6, Main Power Distribution Panel.

 (i)  
Install relay, R7434, in the P415, Right Power Distribution Center.

 S 715-033
 (4)  Make sure that the upper right pitot probe strut heater operates:
 (a)  
Remove relay, R7432, from the P415, Right Power Distribution Center.

 (b)  
Close 6D35, PROBE HEAT IND R and 6D31, PROBE HEAT PITOT R circuit breakers on the P6 Main Power Distribution Panel.

 (c)  
Open 7H8, GND SAFETY RELAY circuit breaker on the P7, Overhead Circuit Breaker Panel.

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

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

 (f)  
Close 7H8, GND SAFETY RELAY circuit breaker on the P7, Overhead Circuit Breaker Panel.

 (g)  
Open 6D35, PROBE HEAT IND R and 6D31, PROBE HEAT PITOT R circuit breakers on the P6, Main Power Distribution Panel.

 (h)  
Install relay, R7432, in the P415, Right Power Distribution Center.

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747-400 MAINTENANCE MANUAL
 S 715-034
 (5)  Make sure that the upper right pitot probe heater operates on the ground with an engine on signal:
 (a)  
Remove relay, R7434, from the P415, Right Power Distribution Center.

 (b)  
Close 6D35, PROBE HEAT IND R and 6D31, PROBE HEAT PITOT R circuit breakers on the P6, Main Power Distribution Panel.

 (c)  
Hold the S2 switch on the YMLA005 ENG 3 N2 speed card in the forward electrical systems card file to TEST.

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

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

 (f)  
Hold the S2 switch on the YMLA005 ENG 3 N2 speed card to NORMAL.

 (g)  
Alternative steps to do a check of the probe heater operation: 1) Hold the S2 switch on the YMLA005 ENG 1 N2 speed card to

 TEST. 2) Measure the voltage at Pin B1 of Relay socket DR7432. 3) Make sure the voltage measurement is from 60 to 65 volts,
 with a digital multimeter on the AC scale. 4) Hold the S2 switch on the YMLA005 ENG 1 N2 speed card to NORMAL.
 (h)  
　
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