Why is my Mercedes battery draining?

One of the major culprits is it’s simply an old battery. The average lifespan of a car battery is only four to six years, so if you’re in that range or over, it’s probably time for a new battery. However, if this isn’t the case, there’s some other mischief going on.

What causes a battery to drain over night?

This can be a result of various factors including the number one cause which is leaving headlights, glove box lights, or cabin lights on overnight. Parasitic drain can also be caused by defective fuses, bad wiring, and poor installation of a new car battery.

How do you check for parasitic drains?

How To Diagnose the Battery Drain

1. Step 1: Remove Negative Battery Cable. Negative Cable Removed.
2. Step 2: Check the Draw Across the Negative Cable and Battery Post.
3. Step 3: Remove and Replace Fuses.
4. Step 4: Isolate and Fix the Issue.
5. Step 5: Replace Negative Battery Cable.

Why does my car have a short that drains battery when sitting overnight?

There may be a problem in the starting system. A short circuit may cause excessive current draw and drain your battery. Check the charging system for a loose or worn-out alternator belt, problems in the circuit (loose, disconnected or broken wires), or a failing alternator.

Can a alternator drain your battery?

How A Bad Alternator Can Drain a Battery. Contrary to its purpose, an alternator can drain a battery. It’s rare, but it’s possible. A draw on the battery only occurs if there’s a problem with either a component in the alternator itself or connections to it.

How do you check alternator by disconnecting battery?

If you’re tempted to test an alternator by disconnecting the negative battery cable, don’t do it. A good alternator may indeed keep the engine running without the negative cable, but this was never a good test. In the pre-computer days, you could pull it off without damaging anything.