ME 7.2

P1457

170 A/C Compressor Control - Below Limit

Function
The magnetic clutch of the A/C compressor is supplied with battery voltage via a relay.
The coil of the relay is supplied with battery voltage via the DME relay on one side and connected to ground via the DME control module on the other side. Only the wire from DME control module, pin II/18, to the A/C relay, terminal 85, is monitored during diagnosis.

Diagnosis conditions
- Engine running
- Battery voltage greater than 7 V

P1455 - P1457:

Wiring Diagram







Diagnosis Procedure


1 Check control wire for A/C relay, pin 2, for open circuit.
1. Remove A/C relay.
2. Connect special tool 9637 to wiring harness (DME control module connector).
3. Connect ohmmeter to special tool 9637, pin II/18, and A/C relay, pin 2.

Display: 0 - 5 ohms

2 Check control wire for A/C relay, pin 2, for short circuit to B+.
1. Remove A/C relay.
2. Remove DME control module connector.
3. Connect voltmeter (positive) to A/C relay, pin 2, and ground.

Display: 0 V

If battery voltage is displayed, check wiring harness for chafing and pinching damage.

3 Check control wire for A/C relay, pin 2 (terminal 85), for short circuit to ground.
1. Remove A/C relay.
2. Remove DME control module connector.
3. Connect ohmmeter to ground and pin 2 (terminal 85).

Display: infinity ohms

If 0 - 5 ohms is displayed, check wiring for chafing and pinching damage.