Headlights dim and return.
 

I have a 2004 with headlights that dim barely perceptably and then return after 2-5 seconds and repeat again in several minutes. This has been going on for the past two years at least. It is not a problem as far as driving and having sufficient light is concerned. At first, I thought I was seeing things, the change was so slight. However, I have started paying closer attention to the lights and sure enough, I am sure it is dimming. I have made cursory looks at wiring to make sure I don't have an obvious grounding problem. That dosn't seem to be the case. My real concern is the problem will manifest itself into losing the lights some night on a road trip, (probably in a snow storm).

My question are, do these cars have some type of fusible link that could be overheating, or some other component that culd cause this problem? If not, what other things should I be looking at/for?

I thank you in advance for any insight anyone can provide!

BTW, I have not been able to determine if it is one light that is dimming or both, as the car does not seem to do it while the car is parked with the lights on. (or at least I have not waited long enough)

The car can command the alternator to shut down when the voltage is good and electrical loads are very small. That's for fuel economy. When the alternator shuts down, the voltage gets a bit lower as the car is running off the battery.

You might be able to duplicate it parked, by running the engine up at similar RPM like driving.

From here, not seeing it firsthand, I can't RULE OUT other problems. But you can hook up a voltmeter & watch the system voltage when driving. Rather than a fusible link, it's got a couple BIG fuses. Attached with screws (not blade-connectors) and they're something like 80 or 100 amps. Check those for dirty/loose/corroded connections??

Thanks for the info.

That makes a lot of sense. The lights dim, but not enough to affect vision. It is an off and on again scenario continuous while driving. I don't notice it much in the summer, but now as the days are shorter, I drive to work in the dark, and often times drive in the evening in the dark.