Circuits

Special Tools
140 589 13 21 00 Quiescent current test adapter 2
201 589 00 99 00 Electrical connecting set
140 589 12 21 00 Quiescent current test adapter 1






Commercially available tools






1 Open fuse and relay box F1 and remove cover.

2 On right engine hood switch (ATA) (S62) keep switch pressed down with insulating tape or lock right engine hood lock with screwdriver.

3 Switch on interior motion sensor if fitted.

4 Lock vehicle.

5.1 Open cover on base module (N16/1) in module box (F23).

NOTE: Vehicles with module box

5.2 Open cover on fuse box (F20) in trunk.

NOTE: Vehicles without module box

NOTE: To prevent incorrect measurements, the switch on the trunk lock must be operated with the trunk lid open or if no switch is fitted, as of approx. 1/95 the left and right trunk illumination bulbs must be removed.

NOTE: Observe current information (A1). First check the circuits of the components which are listed in the Current Information.

6 Remove fuse of the particular component.

NOTE: Only remove the ATA fuse when the vehicle is unlocked (alarm signal).

7.1 Read off quiescent current on the Multimeter connected to the battery and compare with value noted.

NOTE: Vehicles up to approx. 08/95

7.2 Connect measuring cable (6) and test adapter (13) to a second multimeter (12) (measuring range in amperes).

NOTE: Vehicles as of approx. 09.95

8.1 First remove fuse and connect a second multimeter for this and read off the quiescent current after 5 seconds.

NOTE: Vehicles as of approx. 09/95

If the total quiescent current drops <= 0.02A (20 mA):
The unfused circuit is in order.

9 Install fuse again and wait for 5 seconds.
Then check quiescent current at all the fuses as per test steps 6 to 9.

NOTE: After installing the fuse or test adapter there may briefly be a higher quiescent current at the connected components, with the radio of 0.240 A (240 mA).

The higher quiescent current is eliminated by switching the radio on and off.

NOTE: On vehicles with Auto Pilot System (APS) a higher quiescent current of approx. 800 mA occurs after installing the APS computer fusing for the period of the computer run-up (approx. 30 min).

If the total quiescent current drops > 0.02A (20 mA):
Read off again 4 minutes later.
The fused circuit is defective: (down arrow)
Determine fused components with a higher quiescent current.

Specified value of total quiescent current is not reached again: down arrow)
Determine unfused components with a higher quiescent current.

If the total quiescent current rises >0.02A (20 mA):
Determine the cause of the reverse current via a different current path.
Carry out test steps 7.2 to 9.

NOTE: Vehicles up to approx. 08/95