Measurement of the Centre Wire Resistance (CWR) of the OverHeat Detection System (OHDS) Loops

TASK 36-22-00-760-801-A
Measurement of the Centre Wire Resistance (CWR) of the OverHeat Detection System (OHDS) Loops

WARNING: BEFORE YOU INSTALL/REMOVE THE GSE-TOOL, READ THE INSTRUCTIONS IN THE APPLICABLE GSE INSTRUCTION MANUAL. WHILE YOU OPERATE THIS TOOL, CAREFULLY OBEY THEM. IF YOU DO NOT OBEY THE INSTRUCTIONS, INJURY AND/OR DAMAGE CAN OCCUR.

ZONE: 121
ZONE: 122

1. Reason for the Job
Self explanatory
2. Job Set-up Information
A. Fixtures, Tools, Test and Support Equipment

REFERENCE	QTY	DESIGNATION
No specific	1	ACCESS PLATFORM 2M (6 FT) - ADJUSTABLE
No specific	AR	SAFETY CLIP - CIRCUIT BREAKER
20549SI	1	LOOP-CONTROLLER
9240SI	1	CONTROLLER-LOOP
ELC132A	1	LCR METERS
KRTG36-1032	1	BLEED LOOP GROUND TEST

B. Work Zones and Access Panels

ZONE/ACCESS	ZONE DESCRIPTION
121	AVIONICS COMPARTMENT
122	AVIONICS COMPARTMENT
811

C. Referenced Information

REFERENCE	DESIGNATION
TASK 24-41-00-861-002-A	Energize the Aircraft Electrical Circuits from the External Power
TASK 24-41-00-861-002-A-01	Energize the Aircraft Electrical Circuits from the APU
TASK 24-41-00-861-002-A-02	Energize the Aircraft Electrical Circuits from Engine 1(2)
TASK 24-41-00-862-002-A	De-energize the Aircraft Electrical Circuits Supplied from the External Power
TASK 24-41-00-862-002-A-01	De-energize the Aircraft Electrical Circuits Supplied from the APU
TASK 24-41-00-862-002-A-02	De-energize the Aircraft Electrical Circuits Supplied from the Engine 1(2)
TASK 36-11-34-000-001-A	Removal of the BMC
TASK 36-11-34-400-001-A	Installation of the BMC
TASK 36-22-00-100-802-A	Clean the Overheat Detection System (OHDS) Connectors and Apply the Electrical Insulating Compound
TASK 36-22-00-200-803-A	Wetting Current Procedure
TASK 52-41-00-010-002-A	Open the Avionics Compartment Doors for Access
TASK 52-41-00-410-002-A	Close the Avionics Compartment Doors after Access
CWR Connections
CWR Table

3. Job Set-up
Subtask 36-22-00-860-065-A

A. Aircraft Maintenance Configuration
(1) Energize the aircraft electrical circuits
(Ref. AMM TASK 24-41-00-861-002).

Subtask 36-22-00-865-068-A

B. Open, safety and tag this(these) circuit breaker(s):

PANEL	DESIGNATION	FIN	LOCATION
** ON A/C ALL
49VU	AIR BLEED/ENG 2/MONG	3HA2	D12
49VU	AIR BLEED/ENG 1/CTL	2HA1	D11
122VU	AIR BLEED/ENG 1/MONG	3HA1	Z23
122VU	AIR BLEED/ENG 2/CTL	2HA2	Z22

Subtask 36-22-00-010-054-A

C. Get access to the avionics compartment.
(1) Put an ACCESS PLATFORM 2M (6 FT) - ADJUSTABLE in position at access door 811.
(2) Open access door 811 to get access to the main avionics compartment (Ref. AMM TASK 52-41-00-010-002).

4. Procedure
Subtask 36-22-00-760-050-A

A. Maintenance Procedure
(1) Remove the Bleed Monitoring Computer (BMC) (1) that controls the loop that you will measure (Ref. AMM TASK 36-11-34-000-001).

NOTE: BMC 1 controls the zones loop A and loop APU. BMC 2 controls the zone loop B.

(2) On the centre wire resistance table, do a check of the specified pins for the applicable loop.
(3) Connect the test leads of the ELC132A LCR METERS between the pins identified on the specified rack connector(s).

NOTE: You can also use the 9240SI CONTROLLER-LOOP or the 20549SI LOOP-CONTROLLER or the KRTG36-1032 BLEED LOOP GROUND TEST as an alternative to the ELC132A LCR METERS.

(4) On the ELC132A LCR METERS, select the R series function and a frequency of 1 KHz.
(5) Measure the centre wire resistance on the loop between the start pin and the end pin:
(a) Make sure that the measured value is stable.
(6) Make sure that the measured centre wire resistance value is lower than the maximum permitted centre wire resistance value for the applicable loop:
(a) If the measured centre wire resistance value is higher than the maximum permitted centre wire resistance value for the loop:

Do the wetting current procedure (Ref. AMM TASK 36-22-00-200-803).

(b) If the wetting current procedure is not sufficient to get the maximum permitted centre wire resistance value:

Clean the OverHeat Detection System (OHDS) connectors and apply the electrical insulating compound (Ref. AMM TASK 36-22-00-100-802).

(7) Install the BMC (1) (Ref. AMM TASK 36-11-34-400-001).

5. Close-up
Subtask 36-22-00-410-056-A

A. Close Access
(1) Make sure that the work area is clean and clear of tools and other items.
(2) Close access door 811 (Ref. AMM TASK 52-41-00-410-002).
(3) Remove the access platform(s).

Subtask 36-22-00-865-069-A

B. Remove the safety clips and tags and close these circuit breakers in this sequence:

PANEL	DESIGNATION	FIN	LOCATION
** ON A/C ALL
49VU	AIR BLEED/ENG 2/MONG	3HA2	D12
49VU	AIR BLEED/ENG 1/CTL	2HA1	D11
122VU	AIR BLEED/ENG 1/MONG	3HA1	Z23
122VU	AIR BLEED/ENG 2/CTL	2HA2	Z22

Subtask 36-22-00-860-066-A

C. Aircraft Maintenance Configuration
(1) Put the aircraft back to its initial configuration.
(2) De-energize the aircraft electrical circuits
(Ref. AMM TASK 24-41-00-862-002).

[Rev.10 from 2021] 2026.04.01 01:16:34 UTC