Testing quiescent current consumption - ra540b1401030x(1030)

WARNING: This page does not describe the selected car, but rather 42 other vehicles, including the 1999 Mercedes-Benz S600, 1999 Mercedes-Benz S500, 1999 Mercedes-Benz S420, 1999 Mercedes-Benz S320, and 1999 Mercedes-Benz CL600. However, it is still accessible from the selected car via links, so may be relevant.

B. Determining circuit with increased quiescent current consumption Model 140

Preliminary work:

Testing battery charge state.

All assemblies and components in vehicle operating properly.

Operation no. of operation texts and work units or standard texts and flat rates:

B. Determining circuit with increased quiescent current consumption

Preliminary work:

Total quiescent current consumption tested (A).

Preparing for test

Remove cover (7) on fuse and relay box (F1)

Fig 1: Identifying Cover, Fuse And Relay Box

Courtesy of MERCEDES-BENZ OF NORTH AMERICA.

NOTE: In event of complaint that quiescent current is too high when vehicle is locked (A, test step 3).

Perform following steps in addition:

On vehicles with anti-theft warning system (ATA):

Lock hood lock on right (4) with screwdriver.
If present, switch on passenger compartment protection.
Lock vehicle.

Fig 2: Locking Hood Lock

Courtesy of MERCEDES-BENZ OF NORTH AMERICA.

Unscrew screws (8) and lift cover (9) off of module box (F23).

Check seal (10) for damage, replace, if required.

When reinstalling cover (9) ensure that the gasket (10) is seated properly.

Fig 3: Identifying Module Box, Screws, Seal And Cover

Courtesy of MERCEDES-BENZ OF NORTH AMERICA.

Open cover (11) on base module (N16/1).

Fig 4: Identifying Cover And Base Module

Courtesy of MERCEDES-BENZ OF NORTH AMERICA.

Open cover (12) on fuse box (F4) in trunk.

Fig 5: Identifying Cover And Fuse Box

Courtesy of MERCEDES-BENZ OF NORTH AMERICA.

NOTE: In order to avoid erroneous measurements it is necessary to actuate the switch on the trunk lock with the trunk lid open or, if switch is not present as of approx. 1/95, remove the trunk illumination bulbs on the left and right.

Fig 6: Identifying Trunk Lock

Courtesy of MERCEDES-BENZ OF NORTH AMERICA.

TEST STEP 1

	Pay attention to Information Update! Check circuits listed in Information Update first.
Fuse	remove.
	NOTE: Remove fuses for anti-theft warning system only with vehicle unlocked (alarm signal). Remove fuses for auto pilot system last!
Quiescent current	read off on multimeter (2) connected to battery and compare with value noted.
	If total quiescent current drops by < 0.02 (20 mA):
Fuse	reinsert. Perform test in same manner with all fuses in fuse boxes and in base module. Wait 5 seconds between each test.
	NOTE: After inserting a fuse the quiescent current for the connected components may be higher briefly. For the radio this may be as much as 0.240 A (240 mA). This high quiescent current consumption can be eliminated by switching the radio on and off again. After inserting the fuses for the auto pilot system (APS) the quiescent current increases by approx. 600 mA; a waiting time of approx.30 minutes must then be observed.
If no fault is found when performing these tests	proceed with D.
	If total quiescent current drops by more than 0.02 A (20mA): Replace the component listed in the Information Update or continue with C. NOTE: After replacing the component listed in the Information Update, check total quiescent current consumption again (A). On vehicles with anti-theft warning system unlock engine hood lock on right. If the total quiescent current increases to > 0.02 A (20 mA): Cause is current returning through another current path. Perform test step 2.

TEST STEP 2

Test cable (6) and test adapter	connect to second multimeter.
Multimeter	switch on (Mode: Amps).
Faulty fuse (from test step 1)	remove.
Multimeter	connect in place of fuse and read off quiescent current after waiting 5 seconds.
	Quiescent current ≤ 0.02 A (20 mA): Fused circuit okay. Reinsert fuse, wait 5 seconds and then check all other fuses according to test step 1.
	NOTE: After inserting a fuse the quiescent current for the connected components may be higher briefly. For the radio this may be as much as 0.240 A (240 mA).
	This high quiescent current consumption can be eliminated by switching the radio on and off again.
	After inserting the fuses for the auto pilot system (APS) the quiescent current increases by approx. 600 mA; a waiting time of approx. 30 minutes must then be observed.
	Quiescent current >0.02 A (20 mA): Determine fused components whose quiescent current consumption is too high (C).