Nacelle Latch Doors Proximity Switch 3 Failed Open on EIU-1

TASK 73-25-00-810-B65-A
Nacelle Latch Doors Proximity Switch 3 Failed Open on EIU-1

1. Possible Causes

EIU-1 [1KS1]
FAN COWL LATCH PROXIMITY SENSOR HARNESS [4145KS]
FAN COWL LATCH PROXIMITY SENSOR HARNESS [4146KS]
aircraft harness
PROX SWITCH-FAN COWL AFT [4233KS]

2. Job Set-up Information
A. Fixtures, Tools, Test and Support Equipment

REFERENCE	QTY	DESIGNATION
No specific	1	MULTIMETER - STANDARD
No specific	1	PLIERS - JAWED, SOFT

B. Referenced Information

REFERENCE	DESIGNATION
AMM 70-70-00-910-803	SPOP 6 - Cleaning of the Contact Points and Wiring Harnesses
AMM 71-13-00-010-802	Opening of the Fan Cowl Doors
AMM 71-13-00-410-802	Closing of the Fan Cowl Doors
AMM 71-13-00-710-802	Operational test of the Fan Cowl Loss Prevention System
AMM 71-13-22-000-801	Removal of the Fan Cowl Proximity Sensor Switches
AMM 71-13-22-400-801	Installation of the Fan Cowl Proximity Sensor Switches
AMM 71-13-61-000-801	Removal of the Fan Cowl Latch Proximity Sensor Harness (4146KS)
AMM 71-13-61-000-802	Removal of the Pylon Fan Cowl Latch Proximity Sensor Harness (4145KS)
AMM 71-13-61-400-801	Installation of the Fan Cowl Latch Proximity Sensor Harness (4146KS)
AMM 71-13-61-400-802	Installation of the Fan Cowl Latch Proximity Sensor Harness (4145KS)
AWM 715177
AMM 73-25-34-000-802	Removal of the Engine Interface Unit (EIU)
AMM 73-25-34-400-802	Installation of the Engine Interface Unit (EIU)
AMM 73-25-34-860-806	Engine Interface Unit (EIU) DISCRETE INPUTS Menu Data Status
AWM 783609

3. Fault Confirmation
Subtask 73-25-00-710-612-A ** ON A/C NOT FOR ALL

A. Do the operational test of the fan cowl loss prevention system AMM 71-13-00-710-802.
(1) Determine that aft fan cowl latch is faulty.

4. Fault Isolation
Subtask 73-25-00-810-488-A ** ON A/C NOT FOR ALL

A. If there is confirmation of the fault:
(1) With the aircraft in same configuration as required in fan cowl loss prevention system test, check the status of the EIU-1 discrete input.
(a) Make sure that aft fan cowl latch is correctly closed.
(b) Check the status of the EIU-1 discrete input for LATCH DOOR MON SW3 AMM 73-25-34-860-806.
1 If the status of the discrete input is equal to 1:
a Replace EIU-1 [1KS1] AMM 73-25-34-000-802 and AMM 73-25-34-400-802.
(2) If the status of the discrete input is equal to 0:
(3) Open the fan cowl doors of ENG 1 AMM 71-13-00-010-802.
(a) At proximity switch of the aft latch, use a PLIERS - JAWED, SOFT to disconnect connector (4233KS-A) and disconnect connector (443VC1-A) at pylon junction box.
(b) Examine the connectors.
1 Examine the pins and sockets (contacts) for alignment and damage. Look for contacts pushed rearward into the connector face. Replace parts as necessary.
2 Clean the contacts with contact cleaner and clean cloth per SPOP 6. Blow dry with air (at less than 30 psi (2.07 bar)) across connector face AMM 70-70-00-910-803.
3 Reconnect the electrical connectors.
4 Do the test given in Para. 3.
(c) If the connectors are not damaged or if fault continues, use a MULTIMETER - STANDARD to check wiring of aft latch (4233KS) AWM 715177. Refer to table 1. Look for:
1 Wire-to-wire shorts
2 Shorts-to-ground
3 Continuity (less than 5 ohms resistance).

NOTE: A short-to-ground is found when the resistance is less than 100 000 (100K) ohms.

Table 1: Latch No. 3 Connector Contacts

(4233KS-A) Connector Pins	(443VC1-A) Connector Pins
2	23
5	3
3	22

(d) If wiring is not OK, disconnect connector (4056VC-A).
1 Examine the connector.
a Examine the pins and sockets (contacts) for alignment and damage. Look for contacts pushed rearward into the connector face.
b Replace parts as necessary.
c Reconnect the electrical connectors.
d Do the test given in Para. 3.
(e) If the connector is not damaged or the fault continues, check wiring of aft latch (4233KS) AWM 715177. Refer to table 2. Look for:
1 Wire-to-wire shorts
2 Shorts-to-ground
3 Continuity (less than 5 ohms resistance).

NOTE: A short-to-ground is found when the resistance is less than 100 000 (100K) ohms.

Table 2: Latch No. 3 Connector Contacts

(4056KS-A) Connector Pins	(443VC1-A) Connector Pins
3	23
12	3
11	22

(f) If wiring is not OK:
1 Replace FAN COWL LATCH PROXIMITY SENSOR HARNESS [4145KS] AMM 71-13-61-000-802 and AMM 71-13-61-400-802.
(g) If wiring is OK:
1 Replace FAN COWL LATCH PROXIMITY SENSOR HARNESS [4146KS] AMM 71-13-61-000-801 and AMM 71-13-61-400-801.
(h) Connect all connectors.
(i) Do the test given in Para. 3.
(j) If there is no damage on all nacelle connectors and harness until to pylon junction box, check aircraft wiring of aft latch (4233KS) from pylon junction box to EIU-1 AWM 783609.
1 Remove EIU-1 (1KS1) AMM 73-25-34-000-802 and disconnect connector 443VC1-A at pylon junction box of ENG 1.
2 Refer to table 3. Look for:
a Wire-to-wire shorts
b Shorts-to-ground
c Continuity (less than 5 ohms resistance).

NOTE: A short-to-ground is found when the resistance is less than 100 000 (100K) ohms.

Table 3: Latch No. 3 Connector Contacts

(1KS1) Connector AA Pins	(452VT1) Terminal block Pins	(443VC1) Connector Pins
	F	23
8J	3
		22 at ground

(k) If wiring is not OK:
1 Repair or replace aircraft harness AWM 783609.
(l) If wiring is OK:
1 Replace PROX SWITCH-FAN COWL AFT [4233KS] AMM 71-13-22-000-801 and AMM 71-13-22-400-801.
(m) Install EIU-1 (1KS1) AMM 73-25-34-400-802.
(n) Do the test given in Para. 3.
(o) If the fault continues:
1 Replace EIU-1 [1KS1] AMM 73-25-34-000-802 and AMM 73-25-34-400-802.
2 Do the test given in Para. 3.

5. Close-up
Subtask 73-25-00-860-210-A ** ON A/C NOT FOR ALL

A. Put the aircraft back to its initial configuration.
(1) Make sure that the work area is clean and clear of tools and other items.
(2) Make sure that the fan cowl doors are correctly closed AMM 71-13-00-410-802.

[Rev.8 from Aug 2018] 2026.04.04 04:36:55 UTC