What are the problems in the 2014 Mercedes Benz C 300?

This blog will list all the problems in the 2014 Mercedes Benz C C300. We also take a closer look at each of the causes of each problem and their possible remedies. 

What are the problems in the 2014 Mercedes Benz C 300?

The problems in the 2014 Mercedes Benz are listed below:

  • Vehicle not starting (red battery warning)
  • Auxiliary battery malfunction
  • Gear not shifting
  • Water saturation inside the vehicle
  • Media control system touchpad crack
  • Holes and cracks in the driver seat cushion cover.

Mercedes Benz launched the new generation of C Class in 2014. It introduced the fourth generation of drive authorization systems and a more lightweight aluminium build.

Mercedes Benz rectified the problems like E-OBD and ABS/ESP inoperative malfunctions in the new generation of C Class W205. the new C 300 had its own share of new problems. Let’s take an in-depth look at each of them:

Vehicle not starting (red battery warning)

The 2014 C 300 was powered by a 2.0-litre M274 inline 4-cylinder engine. It was the first engine with an all-electric coolant water pump. The air conditioning compressor and the alternator are the only components driven by the crankshaft.

The alternator is mounted under the liquid-cooled intercooler and it did not charge the main battery due to an internal malfunction. When the vehicle is running and the main battery is not getting charged from the alternator, a red warning message is displayed to warn the driver that once the main battery is completely discharged, the vehicle will turn off.

The 2014 C 300 had a 70 Ah main battery and it kept the spark system working for a few minutes until it was completely discharged. The alternators also had many problems with the overheating stator coil, worn-out brushes and fault regulators. In some works, the alternator also caused a fire in the engine compartment. The intake manifold and the electrical wiring harness were also damaged due to the fire in the overheated alternator.

The only remedy is to renew the alternator according to the main battery specification of the vehicle. If the main battery installed in the vehicle has a higher capacity battery then an alternator with a suitable capacity must be installed in the vehicle. 

Auxiliary battery malfunction

The 2014 Mercedes Benz C 300 has a main battery to start the engine and supply power to the onboard electrical systems of the vehicle. But a small capacitor is introduced into the onboard electrical network to engine the parking gear if the main battery is discharged or disconnected.

The engine cut-off (ECO) function is no longer dependent on the auxiliary battery; a voltage sag protector keeps the voltage drop in the main battery to only  2-2.5 Volts. Therefore, the main battery is still able to keep the onboard electrical systems powered up while the engine is starting.

The front signal acquisition and actuation control unit is monitoring the voltage of the C1 capacitor and if the voltage level is not within the specified range of 12-14.5 V, auxiliary battery malfunction is displayed in the instrument cluster.

The remedy is to replace the capacitor and also check the capacitor fuse as it is also likely to blow when the capacitor malfunctions. The C1 capacitor is located in the front passenger footwell and replacing the capacitor can take 1- 2 hours.

Gear not shifting 

The 2014 C 300 came with a Mercedes Benz 7 G Tronic transmission. As the C 300 has an ECO start-stop function, the 7 G Tronic transmission needs an auxiliary oil pump in order to keep the automatic oil circulating on the transmission.

The electrical auxiliary oil pump is located below the torque convertor housing and two rubber seals protect the inlet and the delivery outlet from the auxiliary pump. The auxiliary oil pump has a control unit that communicates with the engine control unit over a CAN bus network.

As the electrical auxiliary oil pump is exposed to the elements, an internal electrical short circuit happens in the control unit of the pump and the engine control unit no longer communicates with the transmission control unit over the disturbed CAN bus network.

The 2014 C 300 cannot be shifted into D until the auxiliary oil pump is isolated from the drivetrain CAN network. The remedy is to replace the electrical auxiliary oil pump and restore the communication of the drivetrain controller area network bus.

Water saturation inside the vehicle.

The 2014 C 300 had many reports of water saturation inside the vehicle, especially in models in the international markets. The evaporator drain leaks water into the vehicle instead of draining it outside the vehicle.

The evaporator is installed in the dashboard and a water drain at the bottom is designed to carry the condensed water outside the vehicle. The drain outlet opens near the transmission tunnel.

This problem is easily rectified by installing the evaporator drain properly but the damage to the electrical wiring harness and control units installed in the footwell is expensive to repair.

Media control system touchpad cracks

The 2014 C 300 came with a touchpad in the centre console. It was connected to the telematics CAN network. The touchpad allowed the driver to control the audio 20 or command media system.

Due to the tight tolerances in the material used for the touch surface, various cracks appeared on the touchpad. There was no accidental damage or stress that caused the touchpad to crack.

It was all due to the manufacturing process used for the touch surface and the remedy is to replace the cracked touchpad. 

The cracked surface did stop the touchpad from registering the touches. The cracks were only on the surface and the control unit continued to function as before. 

Holes and cracks in the driver seat cushion cover

The driver seat cushion cover of the C300 developed holes and cracks. The cause for the holes and damaged seat cushion cover was the improper seat cushion. Mercedes Benz modified the seat cushion so that the plastic frame did not damage the seat cover.

The remedy for this problem is to install the updated seat cushion and cushion cover for the driver-side seat. The seat cover on the front passenger side was okay as it is not under an equal amount of stress as the driver seat.

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This blog listed the electrical and mechanical problems present in the C 300. The C 300 launched in 2014 was a huge improvement over the predecessor model. The updates were not only cosmetic but Mercedes Benz completely redesigned the C Class platform to make it more reliable.