Loss of the Power Supply for the Pitot Probe (PHC 3)

TASK 30-31-00-810-826-A
Loss of the Power Supply for the Pitot Probe (PHC 3)

1. Possible Causes

PHC-3 [6DA3]
wiring between the PHC 3 pin A/S and the ground terminal
wiring between the PHC 3 pin A/A and the circuit breaker (3DA3)
C/B-ANTI ICE/PROBES/3/PITOT [3DA3]
wiring from the PHC 3 (6DA3) pin A/H to the pitot probe 3 (9DA3) pin A/B

2. Job Set-up Information
A. Referenced Information

REFERENCE	DESIGNATION
TSM TASK 24-00-00-810-803-A	Circuit Breaker Tripped and/or C/B TRIPPED Warning
AMM 30-31-00-710-001	Operational Test of the Probe Ice Protection
ASM 303101
ASM 303103
AMM 30-31-34-000-002	Removal of the Probe Heat Computer (PHC)
AMM 30-31-34-400-002	Installation of the Probe Heat Computer (PHC)
AMM 34-11-15-000-001	Removal of the Pitot Probe
AMM 34-11-15-400-001	Installation of the Pitot Probe

3. Fault Confirmation
Subtask 30-31-00-710-100-A

A. Test
(1) Do the operational test of the probe ice protection AMM 30-31-00-710-001.

4. Fault Isolation
Subtask 30-31-00-865-057-A

A. Table of the circuit breakers used in this procedure:

PANEL	DESIGNATION	FIN	LOCATION
** ON A/C ALL
122VU	ANTI ICE/PROBES/3/PITOT	3DA3	Z16

Subtask 30-31-00-810-075-B ** ON A/C NOT FOR ALL

B. If the test gives the maintenance message CHECK PITOT PHC 3 SUPPLY:

Do a check of the status of the circuit breaker (3DA3).

(1) If the circuit breaker is closed:

Do a check for 115VAC at pin A/A of the PHC 3 (6DA3).

(a) If there is 115VAC:

Replace the PHC-3 [6DA3] AMM 30-31-34-000-002 and AMM 30-31-34-400-002.

(b) If there is no 115VAC:

Do a check for a ground signal at pin A/S of the PHC 3 (6DA3).

1 If there is no ground signal:

Repair the wiring between the PHC 3 pin A/S and the ground terminal ASM 303103.

2 If there is a ground signal:

Do a check of the wiring between the PHC 3 pin A/A and the circuit breaker (3DA3).

a If there is no continuity:

Repair the above wiring.

b If there is continuity:

Replace the C/B-ANTI ICE/PROBES/3/PITOT [3DA3] .

(2) If the circuit breaker is open:

Do the procedure (Ref. TSM TASK 24-00-00-810-803).

(a) If the fault continues:

Disconnect the connector from the pitot probe 3 (9DA3) and do a check of the resistance between pin A/B and pin A/C.

1 If the resistance is more than 35,7 ohms (open circuit) or less than 32,3 ohms (short circuit) at a temperature of 20 deg.C (68 deg.F):

Replace the PROBE-PITOT 3 (9DA3) AMM 34-11-15-000-001 and AMM 34-11-15-400-001.

2 If the resistance is between 32,3 ohms and 35,7 ohms at a temperature of 20 deg.C (68 deg.F):

Replace the PHC-3 (6DA3) AMM 30-31-34-000-002 and AMM 30-31-34-400-002.

a If the fault continues:

Do a check and repair the wiring from the PHC 3 (6DA3) pin A/H to the pitot probe 3 (9DA3) pin A/B ASM 303101.

3 If the fault continues:

Do a check for a short to ground at the wiring between the PHC 3 pin A/A and the circuit breaker (3DA3).

a If there is a short to ground:

Repair the related wiring.

b If there is no short to ground:

Replace the C/B-ANTI ICE/PROBES/3/PITOT [3DA3] .

4 If the fault continues:

Replace the PHC-3 [6DA3] AMM 30-31-34-000-002 and AMM 30-31-34-400-002.

Subtask 30-31-00-810-075-E ** ON A/C NOT FOR ALL