Starter fault diagnostics (Mercedes-Benz C-Class W202)

If the starter does not turn, then first of all check whether there is the voltage required for retraction at terminal 50 of the traction relay - at least 8V. If the specified voltage is received, then it is necessary to check the lines that belong to the electrical circuit of the starter according to the electrical diagram. Whether the starter is retracted with full battery voltage can be checked as follows:

do not engage any gear, turn on the ignition;
shunt with a wire (cross-section not less than 4 mm²) terminals 30 and 50 on the starter, see also the wiring diagram Electrical diagram of starter, generator, battery (DD 601/604/605).

If the starter starts normally, then the fault lies in the wires going to the starter. In this case, check the starter with it removed.

Test condition: the connections must be tightened to failure and they must not be oxidized.

CAUSE	REMEDY
The starter does not turn when the ignition and starter switch are activated
The battery is discharged	Charge the battery.
Line 50 to ignition switch and starter is broken, starter switch is faulty	Repair the gap, replace faulty parts.
Broken wire or connection to the body; the battery is discharged	Check battery cables and connections, measure battery voltage, charge battery if necessary.
Insufficient current flow due to loose or oxidized connections	Clean the battery terminals and posts.
No voltage at terminal 50 (traction relay)	Restore the fuse-protected connections between the battery, starter and vehicle body.
The starter turns too slowly and does not start the engine
The battery is discharged	Charge the battery.
The engine does not contain winter or all-season motor oil	Fill with multigrade oil.
Insufficient current flow due to weakened or oxidized connections	Clean the battery terminals and posts and clean the connections on the starter, tighten the connections securely.
Carbon brushes do not fit the commutator, terminals in their contact surfaces are worn, torn, oily or dirty	Check, clean or replace carbon brushes, check contact surfaces.
Insufficient clearance between carbon brushes and commutator	Replace the carbon brushes and clean the contact surfaces of the carbon brushes.
The collector is scratched or burnt and dirty	Turn down the commutator or replace the anchor.
There is no voltage at terminal 50 (minimum 8 V)	Check the ignition and starter switch or solenoid relay.
The traction relay is faulty	Replace the traction relay.
The starter engages and retracts, the engine shaft does not rotate or rotates only in jerks
The gear transmission is faulty	Replace the gear transmission.
The gear is dirty	Clean the gear.
The toothed rim on the flywheel is faulty	Rework the toothed rim, replace the flywheel if necessary.
The gear transmission does not work
The gear or thread is dirty or faulty	Clean the gear transmission, replace it if necessary.
The traction relay is faulty	Replace the traction relay.
The return spring is weakened or broken	Restore the return spring.
The starter continues to operate after the ignition key has been turned off
The traction relay hangs and does not turn off	Turn off the ignition immediately, replace the traction relay.
The ignition and instrument switch does not turn off	Immediately disconnect the wires from the battery terminals, replace the ignition switch and instrument cluster