Measure first, then decide
Is it the battery, the alternator or the starter? We test at your car before anything is replaced
Three different parts produce the same "car won't start" — at three very different prices. The only honest way to tell them apart is to measure. We do it at your car, show you the numbers, and explain the verdict in plain English.
The decision tree we run
- Battery light stayed on while driving, then the car died: alternator territory — the engine was living off the battery.
- Starts after a boost, dead again within a day: charging fault; a new battery alone would be money down the drain.
- Single loud click, bright lights: starter suspect.
- Machine-gun clicking, dimming lights: discharged or dying battery.
- Slow crank on cold mornings only: battery ageing — measurable, and worth catching before the morning it matters.
Symptoms overlap, which is why the answer comes from the meter, not the ear. If you want to understand the logic in depth, the guide battery, starter or alternator? walks through every pattern.
Why we won't just sell you a battery
A third of "dead battery" calls aren't the battery. Replacing it anyway is the easy sale and the wrong fix — the new one drains exactly like the old one did. Our rule is simple: if the test says the fault is elsewhere, we tell you, in writing, with the measurements. If the test says the battery is done, the correct replacement is on the van and can be fitted immediately.
Diagnostic questions
What do you actually measure?
Resting voltage (a healthy 12 V battery shows ~12.6–12.7 V engine off), cold-cranking performance under load, charging voltage with the engine running (~13.8–14.4 V if the alternator is healthy), and the starter’s draw. Four numbers, one clear verdict.
The car jump-starts fine but dies again the same day. Battery or alternator?
That pattern points at the alternator (or its belt): the battery runs the car and never gets refilled. A new battery would “fix” it for a day or two. This is exactly the case the test exists for.
One loud click and nothing — is that the battery?
Often it’s the starter: the solenoid engages (the click) but the motor doesn’t turn. If your lights stay bright during the attempt, suspect the starter rather than the battery. We check both on site.
Do you repair alternators and starters?
No — we diagnose them honestly and fix everything battery-side on the spot. If the verdict is alternator or starter, you get it in writing with the measurements, so any workshop can act on it without re-diagnosing (or re-charging you) from scratch.
What does the diagnostic cost?
A call-out with the diagnosis included, quoted before we set off. If the verdict leads to a battery replacement on the spot, the diagnostic effort is folded into that job — you don’t pay twice. See pricing.