2012 Volkswagen Jetta SportWagen - Headlights Pulse

Dear Car Talk;

What causes headlights to pulse? I have noticed when driving that both the low and high beams (more noticiable on the highs) will randomly pulse. They will quickly go a little brigher and/or a little dimmer. KInd of like a flicker, but the lights never go out. SInce it’s affecting all of hte lights, I hesitate to think it’s stickly a bulb issue. The interval does not seem to have a pattern and it doesn’t seem related to hitting bumps in the road.
Car just had its 50000 checkup, so I wouldn’t suspect the alternator or battery would the culprit. We also just had the CCM replaced by a VW Dealership for an unrelated problem.

That checkup probably included a test of the battery, but it is very unlikely that they tested alternator output.

This is almost surely a case of a failing alternator. You should have the alternator’s output tested before it kills the battery and adds to your repair costs.

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If you can do some DIY, consider removing the alternator and taking it to an auto electric shop. (Call them first and see if they can get on it quickly.) They might be able to test it while you wait, and maybe even fix it in short order. They are likely to know more and do better than other parts or repair places.