Alternator whine

[ejschultz 10+ year member]

Could a dying alternator cause alternator whine? I've noticed in my Jeep lately that I get alternator whine. I didn't have it when I first installed my system. I can tell that my alternator is getting weaker and weaker. My headlights dim when I put my turn signal on (FML). I'm looking into some new alts right now, but I was just curious if that can cause whine.

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[ejschultz 10+ year member]

Well, the alternator whine seems to vary with temperature and possibly humidity. Today, it was warmer than it has been in the last couple of days (when I started to notice the alt whine). There was a little whine this morning, while it was still cooler. As the day progressed, the temperature increased. With the increase in temperature, the alternator whine seemed to vanish. Tonight, it cooled back down, but it's humid like a mofo right now. There was no alt whine on my way home from work. Also, I noticed that my headlights aren't dimming anymore with the turn signal as they were before. Any insight as to what's causing this phenomenon?

 

[helotaxi 5,000+ posts]

Check the battery. Dimming lights is a symptom of a weak battery and the battery is the primary filter for ripple voltage that causes the alt whine noise.

 

[ejschultz 10+ year member]

I'm going to try autozone tomorrow and have them test the alt and battery. I'll see if that's it. If it ends up being one or the other, or both, it gives me a reason to upgrade. //content.invisioncic.com/y282845/emoticons/biggrin.gif.d71a5d36fcbab170f2364c9f2e3946cb.gif

 

[ejschultz 10+ year member]

And.........

The alternator failed. Good news is the battery sits at like 12.5 volts so it's good. The alternator, under a load, only charged at a steady 12.3 volts. I'm going to eventually swap that out and I'm still going to check for any crosses with my power/signal wiring.

 

[helotaxi 5,000+ posts]

With the alt being that weak, the battery isn't going to last long if you drive the car at all.

 

[ejschultz 10+ year member]

I'm normally not giving it a full load to support. Also, if the battery doesn't last, I'll just "upgrade" that too while I'm at it.

 

[helotaxi 5,000+ posts]

I'm still going to check for any crosses with my power/signal wiring.

Power wiring being near signal wiring has nothing to do with noise.

 

[ejschultz 10+ year member]

It can potentially introduce noise into your system. It's not likely, but it can happen.

 

[helotaxi 5,000+ posts]

Physically impossible. Old audio myth that never seems to want to die. DC (your power wiring) cannot introduce noise into AC (your signal cables). For noise to be introduced you would need a fluctuating magnetic field that could induce a voltage in the signal wire. DC does not fluctuate in the manner required.

 

[ejschultz 10+ year member]

That does make sense. Myth or not, I'm still going to do it for sh*ts & giggles.

 

[ejschultz 10+ year member]

Ground loop isolators FTW. I got 2 Fierce Car Audio GLIs from work (BBY) and they got rid of the alt whine and a slight hum I'd get when my headlights are on. They also didn't noticeably adversely affect the sound quality of the system. I wanted to get the PAC GLIs but they're like $15 + shipping everywhere. They have an almost perfectly flat response curve from 20-20000 Hz. The ones I got look identical to the PACs and cost me less than half that for both, not just one. I'd assume they're made by pac because of their styling. There's probably only a few companies out there actually making them anyway.

 

[nateberrier 10+ year member]

I have always run my power cables with my rcas and speaker wires, never any problems. Always a bad ground. Most of the time the bad ground is from people grounding their headunit using the wire harness instead of making one. (lazy)

 

[ejschultz 10+ year member]

Yup, that was probably my problem. Have you ever put a system in a ZJ though? There's so little room inside the dash with which to work. I wouldn't call it laziness in my case though. Making a new ground is not hard, but with the limited room I have in there and limited options I have for running wiring, I decided to get the GLIs. They work rather well. I may still ground the HU somewhere else in the future, but for now, the GLIs will do.

 

[VWBobby 10+ year member]

Another thing that can happen is bad brushes can introduce noise into the system. The regulator smooths most of the voltage spikes out, but the slight ripple it causes makes a hum, especially if you test it with an AM radio. An old trick is to put capacitors on every electric motor to kill the noise at the source.

Its always a good idea to route any wires away from your RCAs.... Anyone who's worked with guitar or pro audio has heard what happens when you introduce noise into a preamp.... While your power is DC, any RF or EMI that is near your input cables can be amplified quite a bit on a 500-watt or higher system, resulting in noise/hum.