Your car won't start. Before you buy a part or call the tow truck, there are three simple tests that almost always pinpoint whether the issue is the battery, the alternator, or the starter. This guide covers them in order of speed. No tools required for the first two.
Why the three get confused
- The battery stores energy and feeds it to the starter during cranking.
- The starter uses that energy to spin the engine until it fires.
- The alternator, once the engine is running, recharges the battery and powers everything else.
Test 1: listen to the crank
Free and instant. Turn the key and listen:
- Single click, then silence — starter is getting power but not turning. Likely: battery too weak, or bad solenoid.
- Rapid clicking ("brrrt") — battery nearly dead.
- Dead silence — dead battery, loose terminal, or blown main fuse.
- Starter cranks normally, engine won't fire — not an electrical problem. Look at ignition or fuel.
- Starts then stalls immediately — alternator not charging.
Test 2: resting battery voltage
Multimeter on the terminals, engine off for at least 20 minutes:
- 12.6V+: fully charged.
- 12.2-12.5V: partial.
- 12.0-12.1V: weak.
- < 12.0V: discharged — recharge and retest.
- < 10V: dead, replace.
Test 3: alternator charging voltage, engine running
Start the car (jump if needed):
- 13.8-14.7V: alternator is healthy.
- 12.5-13.7V: alternator is weak, will fail soon.
- < 12.5V: alternator is dead, replace.
- > 15V: regulator is faulty, replace.
Quick interpretation
| Symptom | Likely cause |
|---|---|
| Rapid clicking | Battery |
| Single click + silence | Battery OR starter |
| Jump-starts, then stalls | Alternator |
| Jump-starts, no restart without jump | Battery OR alternator (Test 3) |
| Dead silence | Dead battery, terminal, or fuse |
| Cranks but won't fire | None of the three — ignition/fuel |
Before replacing a part
Once you've narrowed it down, call us with your make/model/year. In 90% of cases, we confirm stock or order the part for next day.
FAQ
Is it the alternator or the battery?
Jumped and stalls within minutes = alternator. Drives fine but won't restart after shutdown = battery. Test 3 confirms.
My car clicks but won't start — what is it?
Single click = battery too weak OR bad starter. Rapid clicking = battery nearly dead. Try a jump.
How much does an alternator cost?
Typically $150 to $400 for the part.
Need a battery, alternator, or starter?
Also see our winter battery guide, our batteries in Laval page, or our auto parts in Laval.