Mercedes W204 Battery Drain — Comfort Access Module
Mercedes-Benz
C-Class
2007
All
⚡ Quick Summary
Severity Level
Medium
Safe to Drive?
✅ Safe to Drive
Safety Impact
No direct safety impact reported by owners
Urgency Level
🟡 Monitor Closely
The comfort access (keyless entry) module on W204 C-Class stays active scanning for key fobs, draining the battery within 3-5 days if parked without driving. Diagnosis with Mercedes STAR diagnostics. Module replacement or deactivation costs £150-400.
Repair / Solution
No confirmed fixes yet. Share yours below.
⚠️ Wrong Diagnosis?
No commonly reported misdiagnoses for this fault yet. If you have replaced a part that did not fix this Mercedes-Benz C-Class 2007 problem, submit a wrong diagnosis report — it helps other drivers avoid the same costly mistake.
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