Failure of the IDG1 Disconnect Circuit

TASK 24-20-00-810-851-A
Failure of the IDG1 Disconnect Circuit

1. Possible Causes

GCU-1 [1XU1]
RELAY-IDG 1 DISC CTL [3XT]
RELAY-FUNCTION (7XT)
IDG1 disconnect wiring
IDG [4000XU]

2. Job Set-up Information
A. Referenced Information

REFERENCE	DESIGNATION
AMM 24-21-00-720-041	Operational Test of the IDG Disconnect and Reconnect (Reset) Function - Engine in Operation
ASM 242101
AMM 24-21-51-000-040	Removal of the Integrated Drive Generator - IDG 1(2)
AMM 24-21-51-400-040	Installation of the Integrated Drive Generator - IDG 1(2)
AMM 24-22-34-000-001	Removal of the GCU-1(2)
AMM 24-22-34-400-001	Installation of the GCU-1(2)

3. Fault Confirmation
Subtask 24-20-00-700-100-A ** ON A/C NOT FOR ALL

A. Test
Not applicable, you cannot confirm this fault on the ground.

4. Fault Isolation
Subtask 24-20-00-810-089-B ** ON A/C NOT FOR ALL

A. If the fault symptom is identified by the CFDS message: CHECK IDG1 DISCONNECT CKT and by the warnings IDG1 OIL LO PR and IDG1 OIL OVHT on the upper ECAM display unit:

replace the GCU-1 [1XU1] AMM 24-22-34-000-001 and AMM 24-22-34-400-001.

(1) If the fault continues:

replace the RELAY-IDG 1 DISC CTL [3XT] .

(2) If the fault continues:

replace the RELAY-FUNCTION (7XT).

(3) If the fault continues:

do a check of the IDG1 disconnect wiring between:
the pin 2 of the circuit breaker (1XT) and the pin B3 of the ELEC/IDG1 pushbutton switch (5XT)
the pin 2 of the circuit breaker (1XT) and the pin A2 of the relay (3XT)
the pin B1 of the ELEC/IDG1 pushbutton switch (5XT) and the pin X1 of the relay (3XT)
the pin A1 of the relay (3XT) and successively the pin A/3B of the GCU1 (1XU1) and the pin A/12 of the IDG2 (4000XU)
the pins B2 and X2 of the relay (3XT) and the ground
the pin A/13 of the IDG1 (4000XU) and the ground
the pin A/14 of the IDG1 (4000XU) and the pin A/6B of the EGIU1 (22XU1)
the pin B1 of the relay (3XT) and the pin A/4B of the EGIU1 (22XU1) ASM 242101.

(a) If the wiring is not correct:

repair it.

(4) If the wiring is correct:

do a check of the resistance between the IDG1 disconnect solenoid and disconnect switch:
between the pins A/12 and A/13 for the solenoid (normal resistance = 5 ohms plus or minus 2.5 ohms at 25°C)
between the pins A/14 and A/13 of the switch (open circuit when the IDG is not disconnected, and closed circuit when the IDG is disconnected).

(a) If the IDG1 disconnect solenoid and/or switch is(are) defective:

replace the IDG [4000XU] AMM 24-21-51-000-040 and AMM 24-21-51-400-040.

Subtask 24-20-00-720-050-B ** ON A/C NOT FOR ALL

B. Do the Functional Test of the IDG disconnect system-engine in operation AMM 24-21-00-720-041.

[Rev.8 from Aug 2018] 2026.04.04 04:26:14 UTC