This is the procedure for checking the RPM Speed Sensor:

Pull Compressor Control Relay (N6) off the 12 pole coupling.

Connect volt meter to poles 9 & 11 of the 12 pole coupling and adjust volt meter to alternating current. Terminal 5 & 7 of the 12 pole coupling remain bridged. Allow engine to run at idle speed approx 750 rpm.

Nominal value: atleast .3V AC

NO

Stop engine and check resistance of the speed sensor (L4) on terminals 9 & 11. Nominal Value 530 to 650 ohms, renew speed sensor if required.

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Zafar
94 E320 58000 Miles