Symptoms
- Starts fine most of the time
- Occasionally clicks, cranks slowly, or does nothing
- Problem may correlate with temperature, time of day, or how long it sat
- Wiggling the key or gently rocking the car sometimes helps
Likely causes
- CommonLoose or corroded battery/ground connectionA connection that's fine most of the time can open up under vibration or temperature change.
- CommonAging battery nearing end of lifeBatteries often fail intermittently before failing completely.
- PossibleFaulty ignition switchA worn switch can make and break contact inconsistently.
- PossibleFailing starter solenoid contactsWorn internal contacts can work sometimes and not others.
- PossibleIntermittent security/immobilizer system faultA flaky antenna ring or module can randomly refuse to recognize the key.
What to do
- Note exactly what happens each time it fails (nothing, clicking, slow crank) since this narrows the cause a lot.
- Check and clean both battery terminals and the engine-to-body ground strap, even if they look okay.
- Try wiggling the key gently in the ignition or moving the steering wheel slightly if the column lock might be involved.
- Track whether failures happen more in certain weather, after the car sits overnight, or after short trips.
- Have the battery and charging system tested even if it seems to hold a charge, since marginal batteries often act intermittent.
- If an immobilizer or security light flickers when it fails, note that for the mechanic; it points toward the key/immobilizer system.
- Ask a shop to check the ignition switch and starter solenoid, since intermittent electrical faults often need a scope, not just a code reader.
- Keep a spare, known-good key on hand to rule out a worn key or fob as the culprit.
Tools and parts
- Wire brush
- Notebook or phone to log symptoms
Group-size car batterySearch: “car battery group size for [year make model]”
When to call a pro
Intermittent electrical no-starts are best diagnosed by a shop with a scope and the ability to recreate conditions; describe exactly when it happens.
Safety
Generally low risk
Generally low risk for a careful person. Stop if anything looks different from what this guide describes.