NeiselDewb

I'm having an issue with my alternator, and I don't know exactly how to explain it..so there's a video of it. I am experiencing symptoms of ac noise leakage while driving. Any ideas? I'm not a voltage expert, but is this a "closed loop" situation? I'm getting massive ac noise differences based on what I'm grounding to..and I don't exactly know how to start working on this.

It's worth noting that this is a new alternator from Nation's, a seemingly reputable alternator manufacturer..and all voltage is within spec, as long as I ground to the battery? I'm at a loss here.

KATOOM

Kudos to the video but this is the way I test it. Never run off the batteries as they act as filters to what you may or may not read. Always run off the alternator post and ground to the alternator housing. In saying that, a bad battery cell will skew readings as well and force the charging system to work overtime, so make sure they're both in tip top condition.

The Alternator should be putting out the correct DC voltage but the PCM is what determines what voltage the batteries see based on a few variables, like IAT and battery temp.

Also, checking the AC voltage at idle is important but to fully understand AC voltage levels, you need to turn on every electronic device in the truck (lights, AC with fan on high, radio, etc.) and then have someone ramp the throttle up to about 2000-2500 RPM while you have you read the tester. The AC voltage will increase significantly as the alternator is loaded, and what it gets to is what you want to know. That said, the hotter it is outside, the AC noise will typically increase.

And I understand Nation is a great company. They offer a 180 amp alternator that uses the OEM diameter pulley so you dont have to change the belt.

NeiselDewb

Heh, did you watch the video? :/ I did ground off the alt and take voltage off the hot pin.

The problem is, grounding off the alt readings come back chaotic. Grounding battery ground to alt hotpin come back perfect voltage and ac noise. The alternator is a week old, and was working in spec a week ago when installed.

I'm trying to figure out how I am getting different voltage when ground off the alt or how to fix the alt ground, which I suspect is getting feedback from a closed loop, but can't seem to find anyone who knows enough about electricity to help me understand it in layman's terms, or how to confirm it.

KATOOM

Yes.....I did watch your video, but I'm wondering if you read what I wrote in my post. What part about what I said are you confused on and what are you wanting to know besides that. If you're not understanding what the alternator is doing then isolate it.

dkenny

did you measure from the battery ground to the alternator case? yes I mean the ground side of the alternator..my best guess is it'll be around 0.6v...when it should be 0.

-dkenny

SIXSLUG

I'm thinkin patdaly and jmartin, maybe alpineram, too may have input on this...

KATOOM knows his shizz ,too.....

AlpineRAM

Well, I think you have a nice ground problem.

You can measure DC voltage between battery minus and alternator case. The closer to zero the better.

And for measuring alternator AC- take a look at your AC readings while your measuring tips are only close to the alt- you see a bit of induced voltage from the alternator. Only way to correctly measure this would be with a shielded cable going like this:

Core to alternator plus, shield to alternator ground. You will need several feet of distance to get a meaningful result.

On a lighter note: It looks like the alternator and the brackets are painted really nicely... isolating the alt from ground.

Mexstan

I also think that you have a grounding problem. Have you tried running a temporary wire from the alternator case to either the engine block or directly to the negative terminal of the battery and then taken new readings?

KATOOM

I dont think we'll be getting a response back..... OP has asked this question on other forums as well and was given the same answers.