Battery flat every morning — multi-stage drain case
A diesel van needs a jump start every morning. Rule out the battery and the charging system first, then measure the sleep current and isolate the circuit responsible.
- Toyota Hilux 2018 · Diesel, manual · 2.4 D-4D
- Estimated duration: 40 min
- Pass mark: 60
- Yes — they reduce your score
Scenario overview
Customer complaint
“If it stands overnight it is completely flat by the morning. It has had two batteries already.”
Initial symptoms
Battery completely flat after standing overnight. Two batteries replaced in six months with no improvement. Vehicle is used daily and covers a reasonable distance. No warning lamps while driving.
Initial observations
Charging system not yet tested. An aftermarket tracker was fitted last year.
Relevant history
Two batteries replaced. No other electrical work recorded.
Scenario
A two-stage case. The first stage is about clearing the obvious causes so the drain measurement is meaningful; the second is about isolating the circuit without waking the vehicle and invalidating the reading.
Learning objectives
- Rule out the battery and the charging system before hunting a drain.
- Measure quiescent current after the full sleep delay.
- Isolate a circuit without waking modules and invalidating the measurement.
- Identify an aftermarket accessory as a legitimate cause rather than a fault.
Diagnostic tools at your disposal
- Battery load test — Battery test
- Charging system under load — Charging test
- Quiescent current after the sleep delay — Multimeter
- Isolate the circuit by removing fuses one at a time — Multimeter
- Inspect the aftermarket installation — Visual inspection
How you are scored
- Relevant diagnostic tests30
- Interpretation of results20
- Final diagnosis25
- Repair selection15
- Final verification10