Last week the alternator went out in our van while were passing through a less-than-desirable part of town. Nothing scary, but it was a long process that took an entire afternoon to get it towed to the mechanic. I'm wondering if it could have been prevented in some way.

We try to be judicious about car maintenance: we take our car in for regular oil changes/inspections according to the manual's schedule. We check the tire pressure monthly. However, this alternator was apparently dying and we didn't realize it until it was completely dead.

I've looked at videos that describe how to check an alternator using a volt meter. They're presmised on a suspicion of a problem with the alternator: flickering lights, difficulty starting, etc. In my case (as far as I can tell), we had no warning that it was about to die.

So, I'm wondering if there is a recommended interval for checking the alternator with a voltmeter even when there is no suspicion of a problem?

2 Answers 2


Alternators generally fail in one of two ways either the voltage regulator quits and it stops charging the battery or the diode fails and it drains the battery when the vehicle isn't running. In both circumstances detection ahead of failure is extremely rare. From a maintenance standpoint there's not much you can do to prevent it as the fail point is in the electronic circuitry and not from a mechanical part. Alternators will fail for other reasons mechanical or otherwise but the 2 reasons I mentioned are the most common and give the least warning.


There's not a lot you can do. Alternators have three main components:

  • Generator
  • Rectifier
  • Voltage regulator

The generator is extremely rugged, and will essentially last forever. That's why refurbished alternators are a thing. There's a couple of bearings and brushes, but apart from those there's no wear. Checking brushes every couple of years may make sense.

When it comes to rectifier and voltage regulator, those are solid state electronics. They will fail suddenly, and there's no check possible that will discover problems ahead of time.

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