W-455 · Elektrika
Electrical Drain And A Battery That Will Not Hold
Posts, belt and alternator before a new battery. Charge lamp on while running means the machine is not charging. Parasitic drain and a wet BCM are X-Type classics.
It Goes Flat In A Few Days
Clean, tight posts under the left cover. Electrolyte where the case still has caps. A green eye means charged on the original style battery; clear or red wants charge or renewal. Then look at the auxiliary belt: glazed, cracked or off means the alternator never got a chance.
- Alternator output: Charge warning lamp on with the engine running points at belt, wiring or the alternator itself. Lamp never on at key-on can be the bulb or that circuit, not a healthy charge system.
- Parasitic drain: Something stays awake after shutdown. Boot lamps, aftermarket trackers, a glovebox switch, or a module that never sleeps. Meter the drain with everything off, then pull fuses one at a time to find the circuit.
- Water and the BCM: Blocked plenum drains soak the passenger footwell and kill the body control module; intermittent drains and random electrics often start there (see A-155).
Jump And Forget Is Not A Fix
A fresh battery on a car that still has a short, a dead alternator or a flooded BCM will be flat again by midweek. Charge on a low-amp trickle when you can, confirm charging voltage with the engine running, then hunt the drain. Audio units with a security code need that code before you disconnect the earth lead.