Loss of the N2 Vibration Indication on Engine 1

TASK 77-30-00-810-807-A
Loss of the N2 Vibration Indication on Engine 1

1. Possible Causes

2. Job Set-up Information
A. Referenced Information

REFERENCE	DESIGNATION
AMM 71-00-00-710-009	Vibration Check
AMM 77-11-20-000-001	Removal of the N2 Speed Sensor
AMM 77-11-20-000-002	Removal of the N2 Speed Sensor .
AMM 77-11-20-400-001	Installation of the N2 Speed Sensor
AMM 77-11-20-400-002	Installation of the N2 Speed Sensor .
ASM 773202
AMM 77-32-34-000-040	Removal of the Monitoring Unit Engine Vibration (EVMU)
AMM 77-32-34-000-042	Removal of the Engine Vibration Monitoring Unit (EVMU)
AMM 77-32-34-400-040	Installation of the Vibration Monitoring Unit (EVMU)
AMM 77-32-34-400-042	Installation of the Engine Vibration Monitoring Unit (EVMU)

3. Fault Confirmation
Subtask 77-30-00-710-059-A ** ON A/C NOT FOR ALL

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

4. Fault Isolation
Subtask 77-30-00-810-055-A ** ON A/C NOT FOR ALL

A. If the Post Flight Report gives the maintenance message ENG1 N2 SPEED SENSOR:

do a check for open or short to ground of the wiring from the EVMU (2EV) to the N2 speed sensor (4001EV) pins AA/8D, 7C to pins CC/1, 2 ASM 773202.

(1) If the wiring is not correct:

(2) If the wiring is correct:

with the cable disconnected from the EVMU (2EV), do a resistance check of the EVMU between:
pins 7C and 8D (40 to 80 Ohms).

(a) If the resistance values are in the specified limits:

(b) If the resistance values are out of the specified limits:

with the connector CC disconnected from the N2 speed sensor, do a resistance check of the sensor between:
. pins 1 and 2 (40 to 80 Ohms)
. pins 1 and 3 (> 10 Megohms)
. pin 1 and the ground (> 10 Megohms)

1 If the resistance values are out of the specified limits:

replace the SENSOR-N2 ROTATIONAL SPD [4001EV] , AMM 77-11-20-000-001 and AMM 77-11-20-400-001.

2 If the resistance values are in the specified limits:

Subtask 77-30-00-810-055-B ** ON A/C NOT FOR ALL