SUPERMAN_00TA

iTrader: (25)

I have a charging system that I need some help with..... The car doesnt charge like it is supposed to. When I first start the car. It charges fine but once warm the gauge reads well below 13volts. What could cause this? I have replaced the alternator and the battery cables with no good results. My battery is an Red top optima and it is relocated in the trunk...It doesn't have any problems starting but the gauge reading worries me. Thanks

sjsingle1

iTrader: (1)

replaced the alt..........thats the first clue

Paul Bell

iTrader: (9)

Is the car not charging the battery? Does your battery go dead? At what RPM does it drop below 13 volts? What accessories (headlights, A/C, etc.) are used?

SUPERMAN_00TA

iTrader: (25)

My battery doesn't go dead..... it drops below 13 at idle once warm.... i have one amp and a electric water pump for my air to water intercooler system. Both items are disconnected while trouble shooting this issue.... Scratching my head.....

Paul Bell

iTrader: (9)

So what's wrong with your car? Sounds normal to me.

Start to worry when your battery goes dead.

astro11271984

iTrader: (5)

have you checked the little wire coming off the alternator

Paul Bell

iTrader: (9)

If the wire was off or broken he'd not be charging at all and have a dead battery.

The volt gauge may not always read over 13 volts.

LT1TA

iTrader: (17)

Will it read lower if there are a lot of accessories drawing power? Especially when more than factory and factory voltage is 13v @ idle?

Paul Bell

iTrader: (9)

Yes. Especially at idle when the alternator is at it's lowest output regardless of what the PCM is telling it.

SUPERMAN_00TA

iTrader: (25)

The voltage drops down to 10 volts...... Thats the problem because Im wondering if this is causing my fuel pressure issues! My two pumps are not keeping up and droping pressure when they shouldnt be! I figure if I fix the voltage issue it may solve my fuel issues if they are related!

Paul Bell

iTrader: (9)

Hmmm that is low.

The stock 100A alternator has like zero output at idle speeds. Have you considered moving to the 140A truck alternator upgrade? While it'll put out more, what's important to you is it puts out at lower RPM's.

LT1TA

iTrader: (17)

This retains same bolt location as the ls alt? I read up on this a while ago and pushed it away in my brain. I had an itch there was a voltage to the pump issue if it wasn't a hose issue.

sjsingle1

iTrader: (1)

truck alt FTW !!!!!

Paul Bell

iTrader: (9)

The larger truck alternator bolts & plugs right in. You will NOT be able to re-use the rear bracket that's used on the stock unit.

Unplug & push aside the single wire plug FIRST or you will break it.

Read through (all) this: https://ls1tech.com/forums/generatio...-failures.html

SUPERMAN_00TA

iTrader: (25)

Part Number?

Paul Bell

iTrader: (9)

There are dozens of bigger alternators that would fit. You'll need to do some work on your own to find what fits. Did you go through the above linked thread?

hardrock21

iTrader: (6)

I'm still fighting a similar issue. The stock alternator dropped to 12.0 volts when warm. Replaced the alternator with a brand new acdelco 145a truck alternator. Problem still existed. Ran new power wires and ground wires, problem remained. Relocated battery to trunk and alternator to top passenger side with modular turbos kit, problem is better, but still there. Put overdrive pulley on the alternator and ran a resisted wire from the exciter pin out on the alt to a 12 v source... I'm still getting down to 13.0v when warm. The added loads should actually boost voltage output contrary to the info in this thread. Headlights on will bump my charging voltage .5 v at first but will also eventually drop to 13v. I've read the voltages with the gauge, logged them, and hooked a dvom directly to the alternator. Eventually I will figure it out, just haven't yet. Fwiw mitchel on demand spec states anything less then 13.5 v and the alternator is considered to not be charging.

sjsingle1

iTrader: (1)

my junkyard truck alt never had a issue......my monster 200 amp truck alt does not have any either..........

Paul Bell

iTrader: (9)

I've also had no problems after upgrading to the bigger alternator. Plus I've added a 28 amp load with dual electric fans.

GM has always made vehicles with the bare minimum in parts. Oil cooler lines that all eventually leak. Manifold gaskets that rot away. Radiators barely capable for the application. Alternators that are just enough, but not more. If they used better and more reliable components that were just a bit more capable, their vehicles would be considered better than what's been the norm for many years: Toyota/Honda/Nissan etc. are better quality/designed/built than GM.

Juan Cisneros

I recently changed my alternator the reason being that my battery was always dead still same issue battery still dies car turns on with a jump or if i charge the battery but as soon as I turn off the car for a while it dies please help !!