Intermittent battery light

TerminatoRS

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Need some guidance here, gents. I'll keep this as to-the-point as I can.

-Red battery light flickered on and off briefly the other day on the way to work. 1st gear blip of maybe 1/3 throttle just to hear the KB. Could not get the light to come back on during the drive home. Chalked it up as a fluke until it did it again yesterday during a similar scenario. But, when I tried to make it happen again, nothing. I even tried it with more of a load scenario from low RPM.
-No, I have no gone WOT for fear the boost-a-pump won't receive enough voltage to supply adequate fuel.
-Alternator is a Powermaster 155A with a 62 or 63mm pulley. I installed it in August of 2017 when the OEM one started whining and giving me the battery light.
-3" s/c pulley (17psi), can't remember if the idler is 90 or 100mm, 2lb crank, all the rest are stock. Tensioner still puts up a commendable fight. I don't recall the belt length, but it's new as of June when the lower was added and there were no indications of slippage during its time on the dyno or while on the street. Knowing the gentleman who installed and tuned it, he would not have hesitated to let me know of any concerns in that regard.
-Battery is a couple seasons old, but hasn't shown any signs of letting go. Car can sit for two weeks and will fire right up.
-I do not have any gnarly accessories that I'm running. JMS boost-a-pump with the Lethal upgraded wiring kit and a 5-channel amp that I never get close to using to its potential.

While it's nearing the end of the fun season around these parts, I do have one last event to attend next weekend and it's a 2.5 hour drive each way with some spirited cruises in between. I'd certainly like to sort this out beforehand and before I start replacing parts, I wanted to see if there may be something I'm missing.

Thank you
 

01yellercobra

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First thing is to check the connections. Make sure they're clean and tight. If those are good most parts stores offer free load testing. At the very least it should give you some peace of mind.
 

BlckBox04

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It's the alternator. I know you have a 155 amp but it's still not enough for our cars, especially with all the mods we(you) have. I just went through something similar and put the 200amp with the wiring upgrade and fixed everything.
 

fivelitrecobra

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Check the voltage on your battery without the car running, then again with it running. You should know pretty quickly if its the alternator or something else.
 

TerminatoRS

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Damn... Any recommendations as far as a replacement? I’m surprised it didn’t have trouble during WOT on the dyno.
 

MG0h3

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Most will say nations or J2fab

But none of this matters if you have a failing connection. It doesn’t just have to be loose either.


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Live Wire

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Check the voltage on your battery without the car running, then again with it running. You should know pretty quickly if its the alternator or something else.
Can you elaborate a little on this. My car just started doing this as well. The first time was under heavy acceleration entering the highway from an onramp, then again just driving on a main road.

My battery is showing 12.7v with engine not running, and 14.4 with engine running. I'm assuming you mean if you don't see 14.4v while running, there's a problem and start there.
 

fivelitrecobra

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Correct. When my alternator was on it's way out, voltage would be 11-12v with the car running. If you're seeing 14.4v your alternator is good.
 

ccq8le

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I have seen this many times and so have many others.... Make sure you have the big 3 wire upgrade and go with a better Alternator.

It's the curse of these cars. Seems to be worse in hot weather.

Keep us posted
 

Live Wire

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Thanks fivelitre.

In regards to the alternator upgrade... if I did decide to upgrade to the J2FAB, is the 185A sufficient for folks with minimal upgrades? By the time you get the cable upgrade thats required, you're already at $470ish. At what point do you determine the 270A is needed?
 

01yellercobra

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Don't forget heat plays a factor. I had an alternator that was fine at first start up. Once things got warm the voltage started dropping. Made it a bit of a pain to troubleshoot.
 

olympic

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1) Check the alternator connections for anything burned, loose, corroded, etc.
2) Wiggle/tug the alt wires while monitoring battery voltage while the car is running(only if you are comfortable doing this and can do it safely)
2) Pull the alt and have it tested, preferrably by a place that can run it through the entire RPM range.
3) J2Fab 185amp is plenty for a mildly modded car.
 

BlckBox04

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Bdubbs

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My recommendation is, buy a quality built alternator the first time.

I've been running a Nations alternator for a few years now with wire upgrade. I'm also running a bigger ground from the engine block to the frame.

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IMAG1010_zpsiotl0b9i.jpg



IMAG1013_zpsquzcrtbi.jpg

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