SevereAffected: 2007-201470,000–120,000 miles

Mercedes-Benz C-Class W204 C220 CDI — Alternator / Smart Charge System Failure

Modern vehicles use smart charging systems to reduce engine load, but the complex regulators on the alternators frequently fail.

Severity

Severe

DIY Difficulty

Moderate

Est. Cost

£250–£450

OBD Codes

P0620P0622

Component Diagram

Electrics

Typical layout and location for the Electrics assembly.

Reference Illustration

Symptoms

Red battery warning light on dashboard
'Charging System Fault' message
Systems shutting down (radio, power steering) as battery depletes
Car fails to start

Root Cause

The internal voltage regulator or diode pack on the alternator burns out due to heat and age. Occasionally, a slipping auxiliary belt causes the issue.

How To Fix

Test battery voltage with engine running (should be 13.8V - 14.7V).
If below 12.5V, replace the alternator.
Always replace the auxiliary drive belt at the same time.
Cost: £250-450

Estimated Repair Costs

Repair Option	Est. Cost (GBP)
DIY (parts only)	£100–£180
Independent Garage	£250–£450
Main Dealership	£400–£720

Other Faults on This Variant

Delphi Piezo Injector Failure

Critical

2008-201230,000–100,000 miles0

Early OM651 engines (2008-2012) were fitted with Delphi piezoelectric injectors that failed so frequently it resulted in a massive global recall and class-action lawsuits.

Air Conditioning Condenser Leak (Stone Damage)

Minor

2007-201440,000–120,000 miles£250–£450

The air conditioning condenser is mounted at the very front of the cooling pack, making it highly susceptible to stone damage from the road, leading to refrigerant loss.

Front Anti-Roll Bar Drop Link Wear

Minor

2007-201430,000–80,000 miles£60–£120

The front anti-roll bar drop links wear out on heavily potholed UK roads, causing an annoying knocking sound at low speeds.

Disclaimer: Repair cost estimates are indicative and based on community data. Always get a quote from a qualified mechanic before proceeding with any repair.