had my alternator go out on me a few months back, and replaced it myself. I must’ve gotten a bad alternator at first, because i had to return that one and get a brand new DLG alternator. Since then, the car runs great for the most part. I get this random rough idle with fluctuating voltage sometimes. I watch the volts jump up and down by increments up to .5 volts, and the rpm’s jump up and down as well, along with all lights of the vehicle flashing. I’m going to include two vids, one of the fluctuating volts and one of the rpm’s jumping and dash lights flashing. Cleaned TB’s but didn’t change.

2007 G35x Sedan (VQ35HR)
Current mods:
Resonated Test pipes
ebay Axle Back
370Z Sway Bar
Homemade Grounding Kit replicating the Z1 grounding kit

Also was getting some codes pertaining to upstream o2 sensors being out of range, so i replaced both with expensive but not OEM sensors. Since then i get the occasional pending lean code. I’m questioning a vacuum leak since i hear some hissing around the passenger side TB.

 

Videos:

Video 1: https://streamable.com/d25cpi

Video 2: https://streamable.com/yydcgp

 

Clean up the wires on the power system, alternator primary and positive on battery (including all the attachment points on the fusible link), engine to chassis bonding jumper from the timing chain to chassis, both ends of the negative battery cable,

 

Having the exact issues you’re having after replacing original oem alternator. I’ve done every test I can possibly think of. Voltage drop across - and +, ac ripple test (although I don’t have an oscilloscope). New battery. 2 alternators. First one was reman second is a Duralast Gold (new), same issues with entire electrical system flickering and surging. All lights across the entire system do this and can be seen (has this thing where it will do this really deep voltage fluctuation that even makes idle blip down momentarily) on analog multimeter jumping 0.5-2.0 Volts at battery terminals when it does it’s deep flicker but lights 100% of the time flicker very slightly with engine running. Engine running only condition and only seems to present itself at low rpm or idle. I’ve disconnected and split test almost everything, no odd ends I can find. It’s a bear to get out but hoping you solved your issue. I’ve been chasing this now for 5 months because it’s freezing here and it’s just now finally warming up enough to work.

 

Dude, we may or may not be the exact same person. I haven’t been able to track down this mystical issue. It literally presents itself at the most random times. I’m also living in buffalo NY so it’s been cold as **** and i haven’t been able to tear into it. I’ve tested all the same things as you, and nothing. My absolute best guess is between two things: 1. The alternator I have has somewhat of a faulty voltage regulator, being that the issue is completely intermittent, and often times fixes itself with a quick restart of the car. 2: The DLG alternator we have purchased puts out a bit more power than the OEM alternator, i know that for a fact. I figured this would be a good thing, being that my lights would already dim a bit when my aftermarket sub kicks. However it’s my suspicion that this increase in power is throwing off the PCMs ability to regulate the alternators output. Maybe the PCM is like hey, we need more juice. Then the alternator kicks on with more output than expected, and the PCM is like, hey we’re good, turn that back off. Then it realizes it didn’t actually charge up to the point where it needed to be, and got a false reading due to that increased output. Then the PCM is like hold on, we need more! Which results in this never ending loop of alternator clicking on and off, flickering all the lights in the vehicle, and overall contributing to the symptoms we’re experiencing. When I restart the vehicle, maybe the starter draws enough juice to get me the f out of that range where the loop begins to occur. That’s my best guess bro, but maybe if we work together here we can get to the bottom of it. Before just now, i didn’t think anyone had this issue except myself. I’ve been running on this alternator for a few thousand miles too, and i feel like if the thing was gonna **** itself it would’ve done it already.

 

Side note, if the scenario #2 is probable, we could possibly benefit from some sort of resistor to get us back into normal output?

 

I had that exact thought reading your reply, we have to be the same guys. I’m on a damned mission to figure this thing out. I also have the same hissing sound on the passenger side of the engine. Tested for vacuum leak with propane with no obvious signs. Smoke test is next in line. We should hop on a call and go over everything, figure out what to test replace, and post everything here for the next guy. You’re the only one I’ve found with my exact issue, same year, same symptoms, same tests, same sounds. Email me!

 

Done, email sent.

 

Gave it a good amount of time before coming back with an update to make sure we have it fixed. Long story short, went to a pull and pay and grabbed an oem alternator off of a g35x and everything is fixed. Figured I’d try it because oem alternators are sitting in the neighborhood of $500+ so spent the $30 to check. Have been going 3 months strong with no issues. Everything is back to normal and we are good to go! Don’t buy Duralast! You’re now ‘the next guy’

 

Built to last, Duralast...

You can have OEM alternators rebuilt, most towns have a motor wind / rebuild shop that rebuilds OEM starters and alternators. Usually it costs the same as buying an off-brand one from a parts house but you are retaining OEM equipment that's been rebuilt to spec buy a local reputable shop.

You can rebuild alternators yourself too if you want. It's not too hard but it can be a pain sourcing QUALITY stuff for things like the voltage regulator.

 

A few months ago, I replaced the alternator on my 2008 G35s. I ordered it from Amazon and installed it myself, making sure to triple-check all connections and grounds. Unfortunately, I experienced the same symptoms as you - fluctuating lights and a rough idle that came and went every 30 seconds or so. Initially, I was reluctant to believe that the new (rebuilt) alternator was the problem, especially since it was difficult to replace by myself. However, after checking the connections again and finding no improvement, I finally decided to order another one. Once I installed the second new (rebuilt) alternator, the problems completely disappeared.

 

Thank you for clearing up my headache on this mystery issue.- latest next guy