nakedpants

Hi,

I need some infos about LS/Truck PWM alternators.

When did GM started to install these on Corvettes, Pontiacs and on trucks?

I read that '05 an up truck alternators are PWM ones. Camaro 2010 and up is PWM as well.

What is needed to make these PWM alternators work?

I read that they need a generator battery control module (GBCM) and body control module (BCM) to even work?

Is this true or are there other ways to make these pwm alternators work and supply a good voltage?

I have a 2008 alternator and a matching ECU but I would like to avoid buying a GBCM or BCM module.

Project GatTagO

iTrader: (7)

Is this just a science experiment? I mean, making the older style alternator is simple and they work very well when wired correctly.

Andrew

nakedpants

I have a PWM alternator in a good shape. So why shouldn't I use it if it isn't much hassle to make it work?

1989GTA

I had/have a PWM alternator that came on my 2007 L92 motor. I wound up converting it over to the 4 pin style voltage regulator. The PWM is a two pin. So I now have a non PWM alternator that is rated at 160 amps. Working just fine. It was just a matter of unbolting and unsoldering the old regulator and bolting(screws) in the new 4 pin regulator and of course the one solder joint.

nakedpants

This sounds interesting, can you give me the part number of the voltage regulator which you used? I have a 2008 L92 PWM alternator so I think I might use the exact same voltage regulator as you did. How much did you paid for the voltage regulator? Did you checked what kind of loading current you have after the conversion? ~ 14.5V?

1989GTA

It starts out around 14.5 volts and seems to settle in around 14 volts after the motor has been running awhile. Here is a link to the voltage regulator I used. By the way you will have to open up the plastic over to clear the 4 pin regulator as it is wider than the 2 pin. No big deal.

http://store.alternatorparts.com/d3579--.aspx

1989GTA

It starts out around 14.5 volts and seems to settle in around 14 volts after the motor has been running awhile. Here is a link to the voltage regulator I used. By the way you will have to open up the plastic cover to clear the 4 pin regulator as it is wider than the 2 pin. No big deal.

http://store.alternatorparts.com/d3579--.aspx

Project GatTagO

iTrader: (7)

If you are going to swap to the older voltage regulator, make sure that you wire the S terminal to the power distribution block.

Andrew

1989GTA

Very good advice and that is exactly what I did.

JoeNova

I just deleted the GBCM module and pinned the alternator's 2 wires into the PCM. Done.

nakedpants

Did you checked your loading current? Do you have 14.5-14V or do you have 13-13.5V?

I read that such "easy" fixes will always result in a lower voltage.

Project GatTagO

iTrader: (7)

I would agree. I bet it runs at a steady 13.7 volts and the output varies as load is applied.

Andrew

1989GTA

I originally had the two pin regulator in my car and 13.8 volts was the best it would do. I don't think it was regulating all that well and the battery went dead a couple of times. That is why I switched to the 4 pin regulator. So far so good.

JoeNova

You guys are right, it runs 13.7-13.8 volts.

Would I have to switch out the alternator itself in order to run 14.5v?
I haven't had problems with the battery dying yet, and its just a lawn and tractor battery.

1989GTA

I had an Optima Red Top battery and I think it needed more voltage than what the regulator was allowing to get a full charge. So in the long run it gave up the ghost. I have a regular style battery in there now and no problems. Also the 4 pin regulator.

Gray86hatch

iTrader: (83)

I have ran dad's car with the two pin connector left unhooked for 5 years. He drives the heck out of it charging at 13.7-8 never had a issue. Radio ac big fans no issues.

Imo not worth messing with.

Tim

Exidous

iTrader: (11)

It running at 13.8v means the PCM isn't actually doing anything. The newer truck alternators(last decade) are self exciting when there is no appropriate signal and default to 13.8v.

Project GatTagO

iTrader: (7)

Tim,

Is there a voltage drop when things are powered on?

Andrew

Gray86hatch

iTrader: (83)

Fully loaded 13.6 is as low as I have seen. Never had a low battery issue

Tim

Don Nguyen

iTrader: (2)

Bumping this thread because I want to see if this statement is correct. Is the wiring diagram on LT1swap that states you simply rewire the two grey and brown wires from the generator battery control module incorrect?