RPCU - Fault

TASK 21-31-00-810-844-A
RPCU - Fault

1. Possible Causes

RPCU 9HL
RPCU RELAY (21HL)
P/BSW-CABIN PRESS/MODE SEL/AUTO [14HL]
wiring
C/B [4HL]

2. Job Set-up Information
A. Referenced Information

REFERENCE	DESIGNATION
AMM 21-31-00-710-003	Operational Test of Manual Mode Selection and Manual Mode Pressure Control and Functional Test of Manual Mode Cabin Altitude/Outflow Valve Position Indication
ASM 213101
AMM 21-31-35-000-001	Removal of the Residual Pressure Control Unit
AMM 21-31-35-400-001	Installation of the Residual Pressure Control Unit

3. Fault Confirmation
Subtask 21-31-00-710-136-A ** ON A/C NOT FOR ALL

A. Do the operational test in the manual mode AMM 21-31-00-710-003 but make sure that on the panel 122VU the circuit breaker RPCU SPLY 4HL is closed during the test.

4. Fault Isolation
Subtask 21-31-00-810-205-A ** ON A/C NOT FOR ALL

A. Fault Isolation and Correction
(1) If the outflow valve does not open automatically during the operational test in the manual mode:
(a) Replace the RPCU 9HL AMM 21-31-35-000-001 and AMM 21-31-35-400-001.
(b) If the fault continues:

Replace the RPCU RELAY (21HL) on panel 96VU.

Replace the P/BSW-CABIN PRESS/MODE SEL/AUTO [14HL] on panel 25VU.

(d) If the fault continues:

Do a check and repair the wiring ASM 213101 from:
the RPCU RELAY (21HL) to ground and to the RPCU (9HL).

(e) If the fault continues:

Do a check for ground at:
the RPCU (9HL)A pins <B, B, C and <I
the RPCU (9HL)B pin F

(f) If the fault continues:

Do a check for 28VDC at:
the RPCU (9HL)A pin A,
the RPCU RELAY (21HL)A pin B1.

(g) If the voltage is not correct:

Do a check for 28VDC at the circuit breaker (4HL) on the panel 122VU.

(h) If the voltage is not correct:

Replace the C/B [4HL] on the panel 122VU.

(i) If the voltage is not correct:

Trouble shoot the electrical power system (Ref. TSM 24).

(j) If the fault continues:

Do a check and repair the wiring ASM 213101 from:
the RPCU (9HL) to the CPC2 (12HL),
the RPCU (9HL) to the CPC1 (11HL),
the P/BSW- CABIN PRESS/MODE SEL/AUTO (14HL) to the CPC1 (11HL),
the P/BSW- CABIN PRESS/MODE SEL/AUTO (14HL) to the CPC2 (12HL),
the RPCU (9HL) to the ENG/MASTER switches (1KS1 and 1KS2),
the RPCU (9HL) to the PARK BRAKE CTL RELAY (1804GL),
the RPCU (9HL) to the LGCIU (5GA1 and 5GA2) and
the RPCU (9HL) to the Air Data/Inertial Reference Units (1FP1, 1FP2, 1FP3).

Subtask 21-31-00-710-138-A ** ON A/C NOT FOR ALL

B. Do the test given in Para. 3.

[Rev.8 from Aug 2018] 2026.04.04 04:38:51 UTC