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2018 Mercedes-AMG C63 — battery dies after the car sits for a weekend

CanyonMom126Community StarterApr 21, 20262018 Mercedes-AMG C63 SNorth Jersey
2018 Mercedes-AMG C63 S, about 119,000 miles. Battery passes a quick test and charging voltage looks normal, but after two or three days parked the car sometimes will not crank. What is the cleanest parasitic-draw test on a modern car that takes time to go to sleep? I am in North Jersey. If I figure it out I will update the thread. What would you check next?
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6 replies

UsedCarDIYer737Community StarterCommunity StarterApr 21, 2026permalink
Ask what changed right before it started. If a shop can't duplicate it on the 2018 Mercedes-AMG C63, bring a video plus freeze-frame data, not just a story. Don't erase codes until someone who can help has seen them. Happy to compare notes if your setup is different. That's my plan before I call anyone.
UsedCarDIYer737Community StarterCommunity StarterApr 21, 2026permalink
Intermittent stuff lies if you only catch it once. Swap the cheap/easy piece first on the 2018 Mercedes-AMG C63 and see if the fault moves. That's the branch I'd chase this week. On “amg c63 — battery dies after the,” that was the fork that mattered for me. If you share a photo of the worksheet, easier to sanity-check. Checking again after work.
ProjectMom166Community StarterCommunity StarterApr 21, 2026permalink
I wouldn't throw parts yet. A pressure test beats staring at a dry driveway if the 2018 Mercedes-AMG C63 is losing coolant with no puddle. That's the branch I'd chase this week. Time, temperature, and whether it's in gear are the notes that actually help a shop. I keep a notes app thread for this now.
WeekendGuy384Community StarterCommunity StarterApr 22, 2026permalink
I hear you, though I'd still want a second check. Get a real battery/charging test on the 2018 Mercedes-AMG C63, not just resting voltage, before blaming a module. You'll know quickly if you're on the wrong tree. That's the sequence I'd use. This is the version I'd tell a friend.
ProjectMom166Community StarterCommunity StarterApr 23, 2026permalink
Not convinced that's the whole story. Loaded-suspension checks on the 2018 Mercedes-AMG C63 catch play that a wheels-hanging inspection misses. That's the branch I'd chase this week. This is from a 2018 Mercedes-AMG C63 in North Jersey with 119,000 miles. Write the result down so the next test isn't a repeat of the last one. Video is ugly but it shows the hesitation.
BatteryScout447Community StarterCommunity StarterApr 22, 2026permalink
This is usually cheaper to test than to guess. Two 2018 Mercedes-AMG C63s can feel identical and have different causes, so measure before you copy someone else's repair. Save the big job until that test fails. This is from a 2018 Mercedes-AMG C63 in North Jersey with 119,000 miles. Stop there until you know. I refuse to clear codes until someone else sees them.
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