12.5 running isn't that good. A fully charged battery should be 12.6v, but 12.5 would be fine as well. When the car is running it should start out at 14.6 or so to start recharging the battery and then drop down to say 13.6 or so. So it doesn't sound as if your alt is putting out the right voltage.

For testing batteries, the dealer uses a computerized load tester. You program the battery size and it will apply a small load, measure how far the voltage drops, then what the voltage goes back up to over a set time (1 minute maybe?) then it does a second, bigger load test for a longer time plus the rest I mentioned. Then it will determine if the battery is bad, almost bad or fine.

It also has a clamp on ammeter to see what amperage the alt. is putting out. My stock LS1 alt. is a 102A unit and it was puting out 91 or so amps under load and high rpms.

 

try 4alterstart.com

2 year warranty and their packaging is great.

personally, spec wise, slightly better than the competition and a much better warranty.

 

my cars idling around 500rpms, i remember hearing somewhere that if you drill the hold in the TB blade to a larger diameter that your idle rpms will increase as well? if it is true, i think the set screw would be better cuz its not permanent, can always go back and readjust it, however on my 01 TA i never noticed a screw on it, not trying to jack the thread

 

I checked mine and it idles at about 800rpm. I could also add a device to create a high idle, of say 1500-2000rpm for those occasions I need it.

 

i got mine from ohio generators im pretty happy with it no problems at all

 

i pretty much figured all that out, thats how i determined my alt was done...we do have the same tester at sears afterall...

 

so will the 235A truck alt at 4alterstart.com work?

 

They have a 235 for the LS1. These cars use the CS-130D case. I don't know what the trucks use.

 

for some reason i cant find an ls1 alternator other than the stock one on their site, i figured the truck ones being genIII/IV would be the same alt. can anybody clarify or link me to the ls1 alt.?

 

Look under the Pontiac listing on the left.

 

i dont know what the hell is wrong with me but i just cant find it...

 

http://stores.ebay.com/Alterstart_Po...QQftidZ2QQtZkm

 

oh the ebay store, it all makes sense now, thanks...

 

ok got the new alternator in, its a 235A from alterstart. i noticed on the old alternator the wire was pretty burnt up and the plastic part of the alternator looked like was melting at some point. i'm surprised any current managed to pass through the wire, it was all 4ga already though...

 

That's the one I'm favoring getting. Give us a review if you can.

 

well when the car starts up cold it sits at around 15.5 volts, i checked it at work with our tester, and believe me the headlights and **** seem real bright. eventually it rests at ~14.3. but no dimming or anything now, the voltage still jumps around according to the capacitor, not too accurate, and the gauge in the cluster doesnt move at all now, not so accurate either, i'd say this thing is doing its job.

and at 15 volts the system is extremely loud, makes me wonder if this 400w RMS amp i have is only putting out that much since it is using a 60A fuse and gets louder the more volts i give it, with no distortion that i can hear i might add...

oh and the papers with all the test data that came with the alt state that it hits 250A @ 14.4 volts at 7000 rotor rpms, or ~2333 engine rpms if you have stock pullies...max wattage is 3382, and at idle it should really be putting out around 140-150A

 

Screw those guys.

Cliff notes of long story :
- called to get advise on HA alt for ATI procharged TransAm
- was assured the $299 200a would fit, 'sold hundreds of em'
- several installs/reinstalls, I discover B4C alt housing is too big and causes interference with ATI blower pully
- call and argue with them, they finally say they will exchange it for a stock housing 160a and are reluctant even though I point out the stock size 160a it's being exchanged for is much cheaper
-I ship it back to exchange the one that they assured me would fit for a cheaper 160a stock housing alt
- they charge me $60 because the returned unit was supposedly "damaged in shipping", and they charge me shipping costs for both returning the old alt and sending out the new one (which I expected)
- the new one arrives with a note that says "warranty void" with their ironically useless printed test results - I find out this one fits great but is a piece of **** and chronically drops voltage at idle/caused check gauges lights on the dash/dimming lights, ironic since good idle charge is the reason I bought the f*&king thing in the first place.
- bought $99 new 102amp GM alt and install, problem solved.

I still have their $400+ POS sitting in the floor of my garage.

Buyer beware, if you go there hopefully you have better luck than I did.

Rob (Bad30th)

 

wow that sucks, mine is holding up good though...

 

I thought they used the stock sized CS-130D housing.
The B4C was the LT1 alternator which is totally different.

 

I must have my terminology wrong, but the first one they sent had a bigger sized housing compared to my '99 stocker (which BTW lasted 8 years and ~60k miles). I installed/uninstalled the bigger one and scratched my head a little before thinking to compare one next to the other (obviously the old one used to fit). There isn't much clearance there for me, it would probably be fine for someone without a blower pully running so close to it with such small clearance to start with.

The new one they sent, although it didn't hold voltage after 5 min of driving, was the stock size housing and fit fine.

Rob (Bad30th)