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Discussion Starter #1 (Edited)
Ive noticed a lot of threads on Starting/Charging sys issues. Here's some quick and dirty theory and diagnostics that any shade tree can handle.

Theory Type stuff
The battery is just there to start the car, and provide some amount of 'stabilization' to the current in the system.

The alternator (generator) Provides power to run the vehicle and its loads, and re-charge the battery. The 04's are internally regulated. 05-06 are a PCM controlled generator to help MPG. Generators are a 3 phase AC generator with a diode stack rectifier to convert AC to DC.

The starter turns the engine. duh.

Wires carry current, aka Amperage. 1A = 6.242 × 10^18 electrons passing a given point in 1 second. Thats a lot.

Some EE's on the board are gonna chide me for this, but were gonna think of Voltage as the 'pressure' in a system. This means Amperage is a measure of flow. Which it is.

Electron Theory is the right theory. Electrons in a circuit flow from Negative to positive. This is why bigger grounds are so effective on cars.

If Current isnt flowing, Voltage isnt dropping. No work is being done, no pressure is lost, nothing changes.

Memorize this: Voltage drop allowable is .5VDC or less. On any circuit, at any time. More or less. There are times when .6 or .7 is ok, but thats because its not causing problems.

Know thy tools
A decent tech (or you when youre done reading this) can get a very good picture of the health of a Start/Charge system in just a few minutes with just a DVOM (Digital Volt/Ohm Meter) if you know what the tool is telling you, and what you are looking for/at.

In the voltage setting, the DVOM is two pressure gauges for the price of one (each lead is its own gauge), and displays the differential between each lead. This can be used to your advantage. And we will.

Test lights are nice. You can buy one, or use any 12v bulb. Need at least a 1-2 ohm bulb to provide a good load. Should not be used on low amperage ECM controlled circuits. Will cook module.

Every decent shade tree should have some type of charger. Tis better to charge slow and low than fast. I like automatics myself, but i blew up a battery once by being young and foolish.

Types of tests

Available voltage: red on pos term of battery. black on neg. aka voltage of the battery. must know this. get it first. also, any blk lead on ground/red on pos DVOM is an available voltage test. This is what avail voltage test looks like, 11.68VDC:

Voltage drop: the amount of voltage dropped between point A and point B in a circuit. usually done over one part of a circuit at a time (ie power side only or ground side only). This test kinda sorta tells you the resistance in the circuit. more than .5VDC, high resistance. drop all available voltage, you have an open. Fun Fact: available voltage test is a voltage drop test. This is a voltage drop test of the ground terminal connetion. I know you can treally see, but the DVOM reads .5mV.

And heres one from the body ground to the battery, also .5mV. 4AWG grounds FTW, son.


Circuit integrity: For most guys, this is where the test light comes out. Do an available voltage test, then hit it with a test light. Source voltage, plus a lit light, the circuit is fine. Can also do a voltage drop instead of test light. Purpose is to make sure wire is not partially broken and can carry voltage and Current. Remember, if current doesnt flow, voltage wont drop.

AC voltage: Yes, an O-scope is nice to have. But If your diodes are dead, your DVOM can tell you. set it to AC volts, and place leads on battery like a normal available voltage test. if you have more than .2VAC present, rectifier is dead/dying.

Parasitic loss: Install a battery shut off switch on the ground post/terminal. set DVOM to 10A setting, and place leads on either side of switch. open switch. otherwise, you may wake systems back up by cutting/restoring power.

Ok Nerd boy, thats all well and good, but how do i use this?

Simple.
Available voltage at battery should be between 12 and 13v with engine off. if its cold, it can be lower. At or below freezing, it can be in the 10.x range. if resting voltage is over 13 v with the engine off for a few minutes, the battery's plates are dissolved. get a new battery.

With the engine running, voltage should come up at least 1VDC. If it doesnt, the alternator isnt lighting off, or the charge wire is fubard. Check voltage at the alt's output post. got it there? check the other wires. If its over 15VDC, the regulator is shot.

Voltage drop all the wires.

Voltage drop the gorunds, Like engine to battery neg, alt case to engine.

Here's one that will bite you: got a hard start? think you may have a bad terminal connection at the battery? DONT UNHOOK IT UNLESS YOU CAN SEE THE CORROSION. Do a voltage drop from the post to the terminal. Unhooking and replacing the terminal in this situation can have you chasing ghosts.

Battery going dead? Check for voltage on the battery. place one lead on a terminal (either one) and the other lead on the battery case at several points around the other terminal. more than .1 or so is bad. Start your parasitic loss checks here.

While were talking parasitic losses. .03A. There or less is where you should be AFTER 30 MINUTES. give the modules time to go to sleep.

If you suspect a bad starter, check available voltage, drop on power wire, and ground drop from starter to engine block.

One last tip:

Check the resolution/range setting on your DVOM. 0V is a perfect reading, and nothing, nothing is perfect. If you dont get at least .001V, youre doing it wrong.

Also, when doing available voltage tests, take your readings compared to the source. IF this means hacking up an old 'stension cord to extend battery power and ground to your test site, do it. Same for voltage drops.

SYSTEM DIAGRAMS
2004, WITH T&O
05/06
 

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Some important notes-
On the GTO (and many other newer cars as well), the starter is not directly controlled by the igniton switch. The switch is an input to the PCM, which in turn controls the starter relay that operates the solenoid. So, although a "no-start" condition may in fact be caused by the common issues that Konnie mentions, there are other possibilities as well that may be beyond the typical DIY'er unless they happen to have a Tech 2 handy.
Also, with regard to the charging system- while the '04 LS1 has a conventional alternator with an internal regulator, the '05-'06 LS2 does not. There is no regulator and field control is done through the PCM.
 

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Discussion Starter #4
Fox, I wrote this up a while back to combat the rash of 'is my starter fucked, the battery is fine' threads. Because it usually turned out to be the battery, or some other issue.

I had planned to cover the more advanced stuff for just in case, but got drunk and forgot. Still, these most common checks are the place to start, and in most cases will find the issue.
 

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I agree in most cases it will be the simple stuff, and people should know how to look for it. But the other complications do need to be mentioned.
 

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Nice write up, too bad the mouth breathers that you wrote this for won't bother, or more likely can't read it anyway.

Nice try and "A" for effort.

:rules:
 

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Discussion Starter #9
added pics, bishes. my apologies for the DVOM that is older than some of our newer members. Some bastage decided they needed my Fluke 88 more than I, and i had to bring it out of retirement. and having 2 F88's is a luxury i just cant afford right now.
 

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added pics, bishes. my apologies for the DVOM that is older than some of our newer members. Some bastage decided they needed my Fluke 88 more than I, and i had to bring it out of retirement. and having 2 F88's is a luxury i just cant afford right now.
Thats why I got one fluke and half a dozen cen -tech ( Harbor freight @ 2.98)

That way I don't get to upset when one let's the smoke out or get's absconded. ;)

The amazing thing is that they all read within ~ 2 % of each other, go figure 2.98 vs 298 or what ever I paid back then for the fluke 15 years back.
 

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Discussion Starter #11
its not the accuracy, its the sampling rate. and some of the advanced features like duty cycle.
 

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Konnie, thanks for the write up. It helped today.
 

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Nice writeup but let's just clear up terminology at little bit.

Generators are old style technology (pre late '60's) and were
designed to output a DC Voltage. They do not need a Reciifier
to convert their output to DC, usually used an external voltage regulator
Advantages: Cheap to make ... Disadvantage: Heavier & Bigger

Alternators make 3 phase AC Voltage and require the Rectifier / Diode
Trio to convert it into DC Voltage. Used external voltage regulators at first,
then went to solid state internal regulators. Works better, less maintenance.
Advantage: Light weight, more power for same size. / Disadvantage: Costs more
 

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Discussion Starter #17
Generator is still the term used by most OE's, including GM.

Look at the circuit diagrams.
 

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They can say what they want on the diagram. For sure your shop manuals & parts list will
call it correctly as an alternator
 

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Generator = fence, alternator = fence post
Same thing. Like konnie said. OE even use 'Generator'. Alternator is just more descriptive.
 

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Discussion Starter #20
The Manual calls it a Generator. Per the Theory and Op section

Beyond that, Its purely a semantic argument. The output is in DC, that makes it a generator. If the rectifier was external, it would be a true Alternator, as it outputs A/C.

Every shop manual or other OE material i have ever touched has called it Generator. What the aftermarket and individuals choose to call it is another thing.
 
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