2018 Mercedes-Benz C-Class electrical problems
severe Owners of the 2018 Mercedes-Benz C-Class have filed 12 NHTSA complaints about the electrical at roughly $850 to repair (U.S. federal records, as of July 2026). Source: NHTSA Office of Defects Investigation. See electrical across all vehicles →
| Model year | electrical complaints |
|---|---|
| 2014 C-Class | 11 |
| 2015 C-Class | 47 |
| 2016 C-Class | 28 |
| 2017 C-Class | 26 |
| 2018 C-Class (this page) | 12 |
| 2019 C-Class | 12 |
| 2020 C-Class | 3 |
| 2022 C-Class | 7 |
The failure pattern owners describe
The 2018 Mercedes-Benz C-Class electrical complaints center on several distinct issues. Many owners received recall notices for NHTSA Campaign 21V058000 but faced long delays—dealers couldn't obtain parts or equipment, and the remedy (over-the-air software update) left owners uncertain whether fixes were applied. Two owners reported SOS system malfunctions; one had the issue persist even after recall service, later attributed to a defective Hermes control unit that warranty did not cover.
One owner found water in the spare tire compartment causing rear turn signals, brake lights, and fuel-door failures. Another reports the vehicle shuts down if not started every 3–4 days, requiring six tows; the dealer treated this as normal behavior.
Additional complaints include a burnt crayon odor at 14k miles (cause undetermined), a sunroof that jams and won't open or close properly, and a check-engine light at 79k miles pointing to a PCV valve needing replacement at $2,300. The owner believes this warrants a recall given reports from other Mercedes owners facing the same repair.
Same Mercedes-Benz C-Class electrical reports on nearby years: 2015 · 2016 · 2017 · 2019
Failure modes owners describe
Communication/Electrical System Software and Component Defects (Campaign 21V058000)
Multiple owners report ongoing issues after recall service under NHTSA Campaign 21V058000, which involved over-the-air software updates. Issues include START/STOP feature failures, rear window operation failures, and SOS system malfunctions. Dealers report extended delays in service, with parts and equipment unavailable, and owners uncertain whether updates were completed.
When: 49,000–85,000 miles; some within 1–6 months after recall notification
Symptoms owners cite: START/STOP feature failed to function; Rear windows failed to raise/lower; SOS warning light illuminated; SOS Not Active message displayed after previous recall service; SOS system failed to operate when tested
Repairs/costs cited: Recall repair involved over-the-air software update; parts distribution delays reported. One owner noted dealer service department photos and auto-body wiring repairs after collision-related electrical damage. SOS system failure later attributed to defective Hermes control unit; manufacturer denied coverage.
Recalls/TSBs owners mention: NHTSA Campaign 21V058000 (Communication, Electrical System); NHTSA Campaign 22V365000 (Electrical System, Communication). Manufacturer offered over-the-air update as remedy; parts unavailable for extended periods. Repair cost for Hermes control unit not covered under warranty.
Electrical System Water Intrusion and Light Failures
Owner reports water intrusion into the spare tire compartment causing multiple electrical faults, including non-functional turn signal and brake lights, and a fuel door that opens independently while driving.
When: 52,800 miles
Symptoms owners cite: Light bulb malfunction message displayed; Rear turn signal lights not operating; Brake lights not operating; Fuel door opening independently while driving
Repairs/costs cited: Dealer diagnosed water in spare tire compartment as root cause; vehicle not repaired.
Battery Drain and Vehicle Shutdown
Owner reports vehicle shuts down and requires towing if not started every 3–4 days. Dealership acknowledges issue but attributes it to normal behavior if car sits unused. Owner towed 6 times and expresses concerns about responsibility and service denial.
When: Not specified; reported after extended periods without starting (airport parking implied)
Symptoms owners cite: Vehicle shuts down if not started every 3–4 days; Excessive battery drain; Multiple towing incidents (6 times)
Repairs/costs cited: Dealership attributed issue to normal operation if vehicle unused for extended period; no repair completed.
Burnt Odor Emission
Owner reports strong burnt crayon odor inside vehicle that makes breathing difficult. Dealer investigated but could not determine cause.
When: 14,000 miles
Symptoms owners cite: Burnt crayon odor inside vehicle; Difficulty breathing in vehicle
Repairs/costs cited: Dealer unable to determine cause; vehicle not repaired.
Sunroof Jamming and Locking Failure
Sunroof jams, stays partially open, or fails to close completely. Once forced closed, it will not open again. Owner reports multiple other Mercedes owners with identical issue and expresses safety concern if sunroof brackets fail.
When: Not specified
Symptoms owners cite: Sunroof jams partially open; Sunroof will not close completely; Sunroof will not open after forced closure; Sunroof fails to lock properly
Positive Crankcase Ventilation Valve Failure
Check engine light illuminated at 79,000 miles; diagnostic testing indicates need for PCV valve replacement. Owner reports high repair cost and states multiple Mercedes owners experience the same failure, suggesting potential pattern warranting recall review.
When: 79,000 miles
Symptoms owners cite: Check engine light illuminated; PCV valve failure indicated
Codes mentioned: PCV valve fault code (specific code not stated by owner)
Repairs/costs cited: PCV valve replacement quoted at $2,300.
Synthesized from 12 NHTSA owner complaints — unverified consumer allegations, summarized for patterns. The verbatim filings appear below.
What owners are reporting 0 most recent
Common questions
How serious is the electrical problem on the 2018 Mercedes-Benz C-Class?
It's a meaningful issue. 12 complaints have been filed and the failure mode causes operational problems for owners. Repairs average $850.
At what mileage does the electrical typically fail?
Based on the 12 complaints filed, electrical issues most often appear around 50,200 miles. Some report problems earlier; some make it well past 150,000 with no symptoms. Maintenance habits matter — vehicles that received timely fluid services and were not regularly overworked tend to last longer.
What does it cost to fix?
Independent shops typically charge around $850 for electrical repairs on this vehicle. Dealer pricing tends to run 20-40% higher. The exact figure depends on the specific failure mode, parts availability, and your local labor rates. If you're outside factory warranty, an extended service contract often covers this category.
Are there any recalls related to electrical?
No active recalls currently cover electrical issues on this vehicle. The complaints filed represent owner-reported failures that haven't risen to the level of a manufacturer-issued recall — but they're still worth knowing about before you buy or budget for repairs.