Test alternator charging current - AR15.40-P-5011SX

ENGINES 156, 157, 272, 273, 275, 276, 278, 629, 642, 651 in MODEL 221 

ENGINES 156, 157, 273, 275, 278 in MODEL 216 

Connection scheme 

Fig 1: Testing Alternator Charging Current

Courtesy of MERCEDES-BENZ USA

	Checking
	Risk of explosion  caused by oxyhydrogen gas. Risk of poisoning and caustic burns  caused by swallowing battery acid. Risk of injury  caused by burns to skin and eyes from battery acid or when handling damaged lead-acid batteries	No fire, sparks, open flames or smoking. Wear acid-resistant gloves, clothing and goggles. Only pour battery acid into suitable and appropriately marked containers.	AS54.10-Z-0001-01A
1	Check tension of poly-V belt
2	Check poly-V belt for wear	Engine 156, 157, 272, 273, 276, 278	AP13.22-P-1352SX
		Engine 275	AP13.22-P-1352SZ
		ENGINES 629, 642, 651	AP13.22-P-1352SXI
3	Check electrical lines to on-board electrical system battery (G1), alternator (G2) and onboard electrical system battery (N82/1) for tight seating and a perfect condition
4	Check freewheel of the belt pulley for alternator mechanically	Only for diesel engines and for engine 157.
5	Open front prefuse box (F32) and check alternator fuse
6	Remove lower engine compartment paneling		AR61.20-P-1105SX
7	Check ground strap between engine and body for tight seating and proper condition
8	Connect up volt ampere tester (079) with current clamp (065) according to connection diagram
	Risk of accident  caused by vehicle starting off by itself when engine is running. Risk of injury  caused by contusions and burns during starting procedure or when working near the engine as it is running	Secure vehicle to prevent it from moving by itself. Wear closed and snug-fitting work clothes. Do not touch hot or rotating parts.	AS00.00-Z-0005-01A
9	Start engine	For vehicles as of 1.6.10 open the driver door so that the alternator management changes over into workshop mode.
10	Test charge current at fast engine revs; apply load to on-board electrical system battery (G1) for this step using volt-ampere tester (079)	Vary load resistance until the maximum load current is achieved; in doing so, the regulation voltage must not fall below 12.7 V. Alternator charging current (G2)
		Engine 156, 157, 272, 273, 275, 276, 278	*BE15.40-P-1001-01I
		Engine 642, 651	*BE15.40-P-1001-01H
		Engine 629 If the charging current lies under the specified value the diode for the alternator (G2) needs checking. See ↓	*BE15.40-P-1001-01J
		Test alternator diodes (G2). The alternator (G2) must be replaced if the diodes are defective, see: See ↓	AR15.40-P-9301-02SX
		Replace alternator (G2):
		Engine 156	AR15.40-P-5032SMG
		Engine 272.946/965/ 975, 273	AR15.40-P-5032SX
		Engine 272.974	AR15.40-P-5032SXH
		Engine 275 (except 275.982)	AR15.40-P-5032SZ
		Engine 275.982	AR15.40-P-5032SXM
		Engine 276	AR15.40-P-5032MMA
		Engine 157, 278	AR15.40-P-5032MMB
		Engine 629	AR15.40-P-5032SXD
		Engine 642	AR15.40-P-5032SXI
		Engine 651	AR15.40-P-5032CD
11	Turn off engine
12	Unclamp volt ampere tester (079) with current clamp (065)
13	Install lower engine compartment paneling		AR61.20-P-1105SX