Rep Power: 0

To preface, I have an 04 Honda Civic EX, 2-dr, manual transmission. Everything on the car is stock EXCEPT the stereo, which is an inexpensive Pioneer I bought for the headphone jack.

My headlights and interior lights flicker intermittently. Sometimes they're completely fine, sometimes it's so bad I can't drive at night. I recently replaced the ELD at a mechanic's suggestion, to no effect. recently, I've noticed two things that I believe are key to the diagnosis:

1. When I turn on the fan, rear defrost or high-beams, the whole electrical system shuts down and reboots. It's worse if I turn multiple things on at once, and a few times I've gotten the car to stall while idling while doing this. Otherwise, I have a totally healthy idle.

2. When the problem is active (remember, it's not consistently dysfunctional, that's why my mechanic hasn't been able to catch it yet) I can detect a high pitched whine that is consistent in pitch with my engine RPM's. The more things that are turned on, like the fan and the rear defrost at once, the louder and more prominent the whine is. When I turn the things off, it goes down in volume until it goes away completely (when everything electrical is shut off.) It sounds a little bit like a quiet turbo, if that's helpful at all.

Lastly, I noticed that nothing actually has to be turned on for the system to flicker. Even if the lights are off, the radio is off, EVERYTHING is off, I can still see my speedometer and tach lighting flickering.

I've already gotten the battery and alternator tested half a dozen times... but like I said, it's possible the problem wasn't active during each test. This issue is frustratingly elusive. Any suggestions or help?

 
Rep Power: 517

Does the battery light come on during any of this?
Are the alternator bolts tight?
Is the belt tight?


An alternator can whine while it is actively charging and producing a large amount of current....Normal, for the most part. Most people don't notice it.

An alternator with a bad voltage regulator or bad diode can HOWL when trying to produce a large amount of current. Might howl while not trying hard too.
Sometimes a bad one will stink really bad too. Sometimes a bad one can produce copious amounts of heat.
The howl is usually obvious.
My grandma could even hear when her alt was headed South and headed to my shop to find out what the noise was.

Disconnecting the 4 wire plug will disable charging and stop the howl, if the alt is causing it.
If the howl and flickering happen at the same time, I'd think the alt is trying to take a poop.

I suggest you attach a voltmeter and monitor battery voltage while you drive. There are more tests like voltage drop testing under a load that could be done to locate bad connections and the like.
Poor connections cause the most trouble when an electrical load is tying to pass through it.
Part of what you described made me think of bad connections. Battery posts, cables, bolted connections on the engine and frame, etc.

The biggest part of actually figuring it out is to get it to act up so it can be tested while broken.

HTH