High Output Alternator Issue...

[ThwopKing]

So i get my 320a alt on my 2003 Tahoe and after getting it in I have a battery light and a notification on the screen for system not charging. I have already done the Big 3, all quality 0ga wire to the amp and good grounds. I also started getting a few other codes from the ecu...I'm guessing its because of the excessive volts. When the battery light comes on it thinks its not charging but its fully charging at 14.8. The company I got the alt from tells me that oh yeah that's normal with a high output unit.
Well I can NOT stand driving around like that. Someone linked me to a harness that plugs in between the alternator and the factory plug, but someone also mentioned I can get a " S" to the terminal and run that to the batteries positive and that fixes it.....so I'm not sure what that is. Can someone shed some light on it.

 

[adriver]

What are you amps at that you need 320amp alt? (wondering if they might be pulling even more than the 320amps).
Just to make sure, is your big 3 wire copper, and what lengths are they/where did you mount them?
Did you go from a 1** size alt to your 320, or was there something bigger than the factory in there already? (if you did this are you using the larger belt?)
I think your 1/0 wire might actually be too small for 320 amps. I would probably want 2/0 or more likely 3/0 size.

(I don't even know if the SUV comes with the smaller alt, or if that's just the pickups).

 

[ThwopKing]

The 32oa was a bit overkill, was going to go with 270a but got this one for a good price. I run all quality OFC 1/0ga wiring and everything is done properly. Didn't need to change the belt size and the tensioner took up what little slack there was. Not getting any belt slip at all. I know the alternator is charging and doing what its supposed to and also have had multiple people tell me, oh yeah it does that whenever you run a big enough H.O. Alternator. But, theres no way im driving around with that annoying light and notification coming across the screen. I did find ,what I thought was someone that could, he supposedly makes a plug-in harness to go between the alt and the factory harness....buuuuut he wont answer my messages now.

 

[Doubeleive]

I have never heard anyone say that was normal nor read any where that said is was normal, and I have been reading up on the matter a lot, the only thing that would make sense was if the alternator was not getting excited enough at idle, so when does this message crop up? at idle or at speed going down the road? how old is your battery? does it hold a load or have you had it load tested? also the alternator could be intermittent enough to trigger the error message. it may be advisable to log the volts/amps somehow with a tech tool and see what it going on exactly.
just my 2 cents, I could be totally wrong but I have never heard that said or read about it being "normal" before

I would maybe even check your alternator wiring harness for a good connection to be sure that is not the cause of the error, heat can make things shrink, in theory then loosing a solid connection

 

[ThwopKing]

yeah someone else mentioned it may be an "excite" issue. I haven't taken it out on the road yet, really installed it twice and didn't even want to drive ti with the lights on and annoying me lol. It test's anywhere from 14.5-14.8/.9 volts given no load or load. Battery tests like brand new but I will eventually going to a larger capacity AGM battery.
Oh and just for reference once the electrical is done being upgraded I'll be running the sub amp at .5ohm for 2250watts to those and then another at least 500 to the front doors,rear doors and dash speakers.

 

[adriver]

You haven't drive it at all? I swear my vehicle has a 5 time learning cycle before it figures out to turn the dash lights off, but I never had any lights when I put on my larger alt.


If your belt is the wrong size, your belt tensioner wouldn't be taking up the slack, the belt would be smaller than it needs to be, and then be too tight. Thus causing too much drag, hence the lights. There are two size belts/alternators for this engine. The smaller belt and alternator use a belt that is 3/4" shorter than the large case alternators which has the pulley in a different location.


I wouldn't call that size alt overkill. You came up with 2750 watts, by 14.8 = 185 amps. 2750/12 =229 amps if you listen while its not running. Another up to 100 or so for the rest of your vehicle if you are running. You didn't even say if this is "stated RMS" or if this is your peak.


You can use larger wire if you want to, it won't hurt to go bigger than needed. I think you might want to check those numbers though and should be running 2/0 or even 3/0 wire for over 300 amps.

 

[ThwopKing]

Wire size I should be good according to GP Audio, hopefully, as I dont want to run all new wiring lol. But as far as driving it with the new one on there even though the lights were on, the 25-30mile trip home from work was not something I would want to do then have something fail on the way home. I get home late enough in the day as it is. Maybe one day I'll try and get it on in the morning and drive it a few ties throughout the day. I may try a smaller belt as well even though the tension seemed totally good. Thanks for the help dude!

 

[adriver]

Sure, but if its the belt, you're about 99% going to need a longer belt. I can't think of any company that would make a 320 amp alt using a small case alt.