Q: On occasion my car cranks slowly. It hasn't failed to start, but I have a feeling that day isn't far away; I've been carrying jumper...

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Q: On occasion my car cranks slowly. It hasn’t failed to start, but I have a feeling that day isn’t far away; I’ve been carrying jumper cables just in case. What’s wrong?

A: Possible causes: a marginal battery, a poor connection in the starting circuit or starter, a charging-system problem, or the battery is being drained while the car’s parked.

If this only happens first thing in the morning, a weak battery or a drain in the electrical system are likely causes. (You could look for a stuck trunk or glove-box light, but other causes are less visible.)

If the slow cranking occurs after driving (engine hot), it’s likely a faulty starter or poor charging. Try this: With the engine speed held a little above idle, note the voltage on the instrument panel or the brightness of the dome light. Fourteen volts or a bright light is a good thing. Now, switch on every accessory you can think of. If the voltmeter drops to 12 volts or lower, or the dome light dims, the charging system may not be doing its job.

These are crude tests. You may need a mechanic.

Try to avoid the need for a jump start, though: Modern vehicles are highly sensitive to jump-starting mistakes, and expensive to fix.

E-mail Brad Bergholdt at under-the-hood@earthlink.net. Sorry, no personal replies.