The Engine Clean approach: confirm the complaint, measure the system and isolate the circuit before components are blamed.
Begin with the battery and charging system
Battery condition, state of charge, terminals, earth paths and charging performance need checking before hunting for a drain. A recently fitted battery can still be discharged, incorrectly specified, poorly connected or repeatedly flattened by another fault.
Some electrical activity after switch-off is normal
Modern vehicles do not become electrically silent the instant they are locked. Control units complete tasks and enter sleep mode in stages. Testing too early can make a normal shutdown current look like a fault.
A drain may be intermittent
A module, relay, light, accessory or network can wake only occasionally. The vehicle may behave for several nights and then flatten the battery. That is why current sometimes needs recording over an extended period rather than checked once with a meter.
Measure before removing fuses
Pulling fuses at random can wake modules, erase the pattern or introduce new faults. A controlled test establishes the current draw, confirms when the vehicle should be asleep and narrows the circuit without disturbing the evidence unnecessarily.
Common questions
Before you book electrical testing
Can a new battery still go flat overnight?
Yes. A new battery will discharge if the vehicle has an excessive parked current draw, charging problem or poor connection.
How long does battery-drain diagnosis take?
It depends on when the fault occurs. Some drains are clear quickly; intermittent wake-ups may require overnight or extended monitoring.
Should I disconnect the battery every night?
That may prevent discharge temporarily but can affect vehicle systems and removes evidence. Ask for vehicle-specific advice before disconnecting it.