Car won't start, just clicks
A single loud click with no cranking means the starter solenoid is engaging but the motor is not turning - either it is not receiving enough current or the starter itself has failed. Rapid machine-gun clicking with dimming dash lights is the classic sign of a flat battery or a corroded terminal that cannot carry starter current. Check battery voltage first: below about 12.2 V at rest or collapsing under 9.5 V while cranking, the battery or its connections are the problem, not the starter.
Urgency
Stop driving
Possible causes, most likely first
- Discharged or worn-out battery
Rapid clicking, dim interior lights that fade when the key is turned. Measure resting voltage (healthy: 12.6 V, needs charging below 12.4 V) and do a load test; a battery that drops below 9.5 V during cranking or is more than 5-6 years old is usually done. - Corroded or loose battery terminals
Lights work normally but there is a single click or nothing when cranking; sometimes everything resets. Look for white or green crust on the posts, try to twist the clamps by hand, and measure voltage drop across each clamp while cranking (should be under 0.2 V). - Bad engine-to-body or battery-to-engine ground strap
Same symptoms as a weak battery but the battery tests fine. Measure voltage between the battery negative post and the engine block during cranking; more than 0.3-0.5 V means a corroded or broken ground strap. - Failed starter motor or solenoid contacts
One solid click, full headlights that do not dim, and voltage at the starter solenoid terminal while the key is held. Worn solenoid contacts or brushes are the cause; tapping the starter body may get it to turn once more, confirming the diagnosis. - Seized engine or hydrolock
Single click, battery and starter are good, but the engine will not turn even with a breaker bar on the crank pulley. Rare, but consider after flooding, a snapped timing belt with valve contact or a long storage period. - Faulty ignition switch, starter relay or neutral safety switch
Sometimes starts, sometimes only clicks or does nothing, often improves when wiggling the key or shifting an automatic to Neutral. Check for 12 V at the solenoid signal wire while the key is in Start; if it is missing or intermittent, trace back to relay and switches.
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What you can check yourself
- Turn on the headlights and try to start: if they dim heavily or go out, the battery or terminals are weak; if they stay bright, suspect the starter.
- Look at the battery terminals for corrosion and try to twist each clamp by hand - any movement means a poor connection.
- On an automatic, shift to Neutral and try again; on any car, try the spare key.
- Check whether the battery is more than five years old (date sticker) and when the car was last driven a long distance.