Power and Ground Distribution: Testing and Inspection

WM 9X00IN Measurement of closed-circuit current

Tools

Closed-circuit current should be measured using the digital multimeter with a long integration time (to filter out voltage peaks).





Digital multimeter

Preparatory work on the vehicle

Information

- Before measuring the closed-circuit current, determine the vehicle equipment (I-numbers) and establish the expected closed-circuit current with the aid of the attached table.

- The closed-circuit current must only be measured on a cold vehicle (engine & brakes).

1. Close all doors and lids on the vehicle.
2. Read out the fault memory and delete the displayed faults if necessary.
3. Disconnect the battery.

Connecting the measuring device

1. Use alligator clips to connect the measuring device to the battery ground and body ground.
2. Remove ground strap from the body and secure against contact with the body. The entire vehicle current now flows through the ammeter.

Measurement

Read off the measured values after the waiting period specified in the table.
1. Switch on ignition for 10 seconds.
2. Switch off ignition.
3. Open the driver's door and close the rotary latch with a screwdriver while the door is open.
4. Lock the vehicle using the central-locking remote control and switch off passenger compartment monitoring (press the button on the remote control twice in one second).
5. Read off the closed-circuit current.

Information

- If the value of the closed-circuit current is higher than the value determined in the table, the cause must be established systematically.

- Recommended troubleshooting procedure: With the measuring device connected, remove the fuses of terminal 30 and the relays successively. Observe the values displayed on the measuring device when removing the fuses and relays in order to detect a reduction in current.

- The measured values can vary by approx. 20%.

- The values listed in the table depend on the condition of the battery, the room temperature, the engine temperature and therefore should only be regarded as guidelines.

Reading off the measuring range:

Read off the measuring range only after at least 35 minutes have passed since locking the vehicle.













6. Connect battery and read out fault memory. Erase any faults if necessary. -> 2X00IN Work instructions after disconnecting the battery 2X00IN Work instructions after disconnecting the battery