Component Tests and General Diagnostics

Measurement Of Closed-circuit Current

Tools










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

Preparations on the vehicle

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

1. Open the front luggage compartment.
2. Close the lower part of the lock of the luggage-compartment lid with a suitable tool - e.g. upper part of the lock with a suitable grip - with the luggage-compartment lid open.
3. Remove the ignition key and lock the vehicle with the key (alarm system is activated).

Connecting measuring device
1. Set the measuring device to the highest possible current measuring device.
2. With two alligator clips, connect the measuring instrument to the battery ground and to the second body ground which is always available for RHD or LHD versions.
3. Remove ground strap from the body and secure against contact with the body. The on-board current now flows via the ammeter.

Measurement
- Select a measuring range which ensures that the pointer of the instrument is in the upper third of the scale, as far as possible. Switch over measuring range without interruption. Read off the measured values only after the waiting period specified in the table.
- Do not switch on any electrical consumers during the measurement (open central locking system, etc.).


NOTE:
- If the value of the closed-circuit current is higher than the value determined in the table, the cause must be established.
- The recommended procedure for troubleshooting: With the measuring device connected, pull off the fuses of terminal 30 and the relays successively. When disconnecting, observe the display values of the measuring device to detect a reduction in current.
- After troubleshooting, screw the ground strap back on to the body in the proper manner.
- The measured values may deviate by approx. 20%.
- The values listed in the table depend on the condition of the battery, the ambient temperature and the engine temperature.

Reading off the measuring range:
- Read off the measuring range only when at least 61 minutes have passed since the vehicle was locked.
















NOTE: After prior disconnection of the battery, terminal 15 must have been connected to the control module at least once.