alternator charging fluctuations

**Linebacker** · 05-06-2015

Hey

So last weekend i changed out my water pump and while i was doing that i decided to switch out the supercharger coupler as well. After i was done i was bolting the alternator back on when i started getting a bunch of sparks.. The neg battery cable just so happened to slowly move back and make contact to the NEG terminal. So after putting everything back together i ran the car and everything seemed good.

This week however i have noticed that when i watch the DIC when its monitoring battery voltage it fluctuates quite a bit and i do not remember it ever doing this before.

When i start the car it will charge at about 14.5... after about 10 min when the engine is at operating temperature and if i am not using anything electrical in the car other than the radio the charge will drop to 12.80.. It will stay at that unless i add something electrical like turning on headlights or a heated seat... than it will go back between 13.5 or 14.5.

If the car is off the battery reads 12.50.. The battery is new and i double checked the connections on the battery and the alternator and everything is good.

So is this normal? or did i mess up the internal regulator when those sparks flew?

**Booba5185** · 05-06-2015

Sounds like either the voltage regulator has damage or one of the rectifier diodes went out. I'm thinking the voltage regulator. Just for sh*ts and giggles, did you check the alt sense fuse in the relay box? Next time put a piece of cardboard up against the terminal on the battery

**Linebacker** · 05-06-2015

no ill take a look at the fuse. so should i go and get a new alternator? i was planning on changing it this summer anyways.. its 10 years old now and i would rather switch out myself than pay a shop in the winter.

**Booba5185** · 05-06-2015

You might be able to upgrade at the same time, what's the year\make\model of your car?

**Linebacker** · 05-06-2015

2005 grand prix gtp comp-g

**Booba5185** · 05-06-2015

You could upgrade to a CS144, they put out a lot more at idle than the stock C130D. You'd need an the alternator (duh), 1999 Camaro 3.8L alternator bracket, the mounting bolts, the plug for the alternator, bigger charge wire (which you should already have), and probably a different sized belt. You'd have to grind a bit on the back of the alternator (not that much, I have pics) to clear the supercharger. It's a beast, and you can upgrade it to 200A later on with normal tools (no soldering). Probably one of the best things I've done to the car:

**Linebacker** · 05-06-2015

would it be worth it on a stock car tho? im not even running an aftermarket stereo lol.

**Booba5185** · 05-06-2015

In my opinion, it would be. You are probably okay with the factory alternator, but I'm one of those "replace it with something better, if you can" guys. The CS130Ds run extremely hot and don't last as long as the CS144s, the CS144s put out more power at idle, etc. The CS130D puts out maybe 60A at idle. The CS144 can put out up to 100 at idle.

Here's the output graph of the CS144.

CS130D:

You have a 125a version, so the graph would be a bit better, but you can see the drastic difference. Let me go look up the pulley sizes...

**Booba5185** · 05-06-2015

At 900 RPM, both alternators are right around 2600RPM. So CS144 should put out ~115A, CS130D puts out ~85-90A (hard to say since the graph doesn't have the 125A on it). I'm actually a bit surprised I thought the CS130D put out less at idle. That said, I still personally do the upgrade. I ran my car for less than 1 song of music (setting up head unit stuff), shut the car off went out and touched the alternator and it was hotter than the engine, lol.

**REDCRAPGP** · 05-06-2015

Lmao Boobas going to talk you into the CS144. He forced me to buy one :/

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**Booba5185** · 05-06-2015

Lol. At least I give info and not just "cuz I said so" I can say I upgraded mine to a 200a then put a smaller pulley on it and with my stereo up to ~60%, blower motor on, and 1 heated seat on I maxed out Orielly's tester at 99A. Most people could use a new tensioner and belt, so why not do it all at once and make it better?

**REDCRAPGP** · 05-06-2015

Now just to find the time to swap it lol

And that's my other problem.. I plan on doing the lim again.. I have everything but I haven't been motivated to do it lol

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**Linebacker** · 05-07-2015

It does sound like a good upgrade but i dont think im going to go through with it. i can always sell the alternator to make some of my money back. i looked in the manual for the alt sense fuse and couldnt see any fuses related to the alternator at all. assuming that fuse is good my only other option is to buy a new alternator right?

**REDCRAPGP** · 05-07-2015

Have it tested first at the part store before you one. Might even save yourself a few bucks buy buying a used one to just an idea.

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**J57ltr** · 05-08-2015

Well you may not like this answer, but I am certain that they do this on purpose. I have been watching this and noticed this in 05' on an Imapla I rented. I rent tons of cars (16 this year). I have noticed the same thing that right after start up its 14.1-7, you drive on the freeway and it will drop to 12.5 if you aren't using any real accessories like AC, heated seats, lights things like that. When you do it usually picks up to 13.5-8 and stays there. The first time I saw that happen I just about crapped myself I was 72 miles from nowhere in Utah. I have noticed this in the Chevy Cruze, Malibu, Impala and Yukon.

I seem to remember an article that mentioned not keeping the whole electrical system at 14v to help increase battery life in hot environments. I have also noticed that the ICM seems to have a built in regulator?

Jeff

**Booba5185** · 05-08-2015

Ya know, I have been hearing about an alternator with a clutch, but I've heard bad things, lol. I didn't think the difference would be that drastic.

**ItHurtz** · 05-08-2015

Mine did the same thing, so I put a voltage booster on

Its normal

**Booba5185** · 05-08-2015

Voltage boosters raise the voltage too much, and can lower the amperage (what really matters) of the alternator.

**J57ltr** · 05-09-2015

Voltage follows current it's simple P=VI, the system adjusts the field to output what it needs. I don't have anything that isn't already regulated like amplifiers. When I do add a system I am using a auxiliary battery and it's not like when I was in my late teens and cruised the drag setting off car alarms anymore. Lol

Jeff