427 Practical hints
What to do if …
Symbol messages
Display symbolDisplay messagePossible cause/consequencePossible solution
ò Replace air filter.The air filter is clogged.Have the air filter checked by an authorized 
Mercedes-Benz Light Truck Center.
#The battery is no longer charging.
Possible causes:
alternator malfunctioning
broken poly-V-belt
Do not forget that the brake system 
requires electrical energy and may be 
operating with restricted capability. 
Considerably greater brake pedal 
force is required and the stopping dis-
tance is increased.
Stop the vehicle in a safe location or as soon as 
it is safe to do so.
Apply the parking brake (page 65).
 Check the poly-V-belt.
If it is broken:
Do not continue to drive. Otherwise the engine 
will overheat due to an inoperative water pump 
which may result in damage to the engine. 
Contact an authorized Mercedes-Benz Light 
Truck Center.
If it is intact:
Drive immediately to the nearest authorized 
Mercedes-Benz Light Truck Center. Adjust 
driving to be consistent with reduced braking 
responsiveness. 
512 Technical data
Layout of poly-V-belt drive
ML 320 CDI
1Coolant pump
2Idler pulley
3Automatic belt tensioner
4Power steering pump
5Air conditioning compressor
6Crankshaft
7Idler pulley
8Generator (alternator)ML 350, ML 550
1Idler pulley
2Idler pulley
3Automatic belt tensioner
4Power steering pump
5Air conditioning compressor
6Crankshaft
7Coolant pump
8Generator (alternator)ML 63 AMG
1Idler pulley
2Idler pulley
3Idler pulley
4Automatic belt tensioner
5Power steering pump
6Air conditioning compressor
7Crankshaft
8Coolant pump
9Generator (alternator)