2003 Mercedes-Benz C-Class Problems: 1 Issues Every Owner Should Know
2003 model year · 2,500+ owner reports · Updated April 2026
According to Au7o's analysis of 2,500+ owner reports, the 2003 Mercedes-Benz C-Class has 1 documented known issues, with 1 rated critical. The most serious is SAM Module Failure ($600-$1,800 repair). The most commonly reported issue is SAM Module Failure with 2,500 owner reports. Across all issues, repair costs range from $600 to $1,800. DIY maintenance guides at au7o.io.
All 1 Known Issues
On the 2001-2007 Mercedes-Benz C-Class, the Signal Acquisition Module (SAM) — essentially the fuse box and body control module — fails due to water intrusion or internal solder joint cracking. Causes erratic electrical behavior including lights, wipers, and windows malfunctioning.
Common Symptoms
- Random electrical malfunctions
- Wipers or lights operate on their own
How to Fix
Replace the failed SAM module (front or rear depending on symptoms). Requires dealer-level programming to code the new unit to the vehicle. Check for water leaks at the windshield cowl area that may have caused the failure.
What Owners Are Using
Parts and tips from 2,500+ owners who fixed this issue
- TipBefore replacing the SAM, check for water intrusion from clogged cowl drains. Fixing the drain leak prevents repeat SAM failures.