Massive alternator noise when starting car

[Staszek]

So I finished my stereo install, tuned it every thing sounded great until I started the car then all hell broke loose.

I have never heard alternator noise that bad. I attached a link to the sound so everyone can hear it, don't mind the music I dont know the stations around here yet because I mostly listen to iphone/sirius and that wasnt hooked up at the time so I picked the first station that had a bit of bass to tune.

So here is the thing, I get zero noise in position one (as expected), a bit of noise in position two, but really almost nothing which you will hear in the video, then when I start it just sounds crazy.

The car is grounded directly to the same location the battery is grounded to on the chassis and the stereo is grounded to the OEM radio ground.

So what are we thinking, the radio ground, or is the alternator going?

https://www.youtube.com/watch?v=dWfUIKynsm0

[Cephas]

Ground loops suck! What does your engine to chasis ground look like? Ever replaced it? You might also want to self tap a ground rather than use the one at the battery. There is a ton of current running through that spot and that could be part of the issue.

I would start with the engine ground and go from there. Bavrest makes a really nice upgraded cable for a great price if you need it.

[george graves]

Silly question but....Why does the video sound like the alternator it'self is making that noise? Or it is coming through the speakers? Hard to tell with the video.

[Staszek]

Silly question but....Why does the video sound like the alternator it'self is making that noise? Or it is coming through the speakers? Hard to tell with the video.

Its possible, but something would have had to change in the past week. Started the car to move it last weekend and there was no noise with the radio off.

[Cephas]

Silly question but....Why does the video sound like the alternator it'self is making that noise? Or it is coming through the speakers? Hard to tell with the video.

I thought it was coming through the speakers. Does the noise still happen when the head unit and amplifier are powered off?

[Staszek]

Noise only happens when the car is on and the radio is on. If the car is running and I turn off the radio it stops. I also tried disconnecting the RCAs from the AMP, no noise when I do that.

I tried a different ground for both the AMP and the Radio, still the same exact noise. I am going to try ground loop isolator, I hope that works, but I am thinking maybe its the amp. I had a 4 channel rockford connected before and I didnt have that noise at all, same connections.

[AndrewBird]

Diode pack in the alternator could have died introducing AC voltage into the system. Measure the voltage at the battery with the engine running. Should be ~14v. Any lower might be a bad alternator.

[Staszek]

Possible, I will check that. Charging seems to be good, I have a built in volt meter in the cluster and when the car is running its always in the high 13's. But I will check that too.

[Cephas]

Hmmm, weird question: does the amp chasis show major resistance to the ground lug?

I think you are onto something in suspecting the amp is at fault here.

[Staszek]

Hmmm, weird question: does the amp chasis show major resistance to the ground lug?

I think you are onto something in suspecting the amp is at fault here.

I am not sure what you mean by that. I think this weekend I am going to swap in the Rockford and see if that does anything.

[Cephas]

You get this sorted out?

You could try hooking up your phone through some rcas directly to the amp to isolate the head unit and rca patch cables too.

[Staszek]

You get this sorted out?

You could try hooking up your phone through some rcas directly to the amp to isolate the head unit and rca patch cables too.

Not yet, I had the dash apart last week so no radio or battery hooked up. Once I finish reinstalling the new dash I will get back to tackling the stereo.

[Staszek]

Fixed, I dont know what it was, maybe I got a bad Planet Audio Amp. I switched it with a 5 Channel Rockford Prime amp and the sound is completely gone with all the same connections. So odd.