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post #3 of (permalink) Old 06-09-2009, 01:44 PM
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Originally Posted by Caver Dave View Post
Delco 3wire of approx. 55A of unknown origin. IIRC, "sense" circuit is wired to alt. output?)
Should be a Delco Remy 10 SI alternator,
This is how you find out EXACTLY what your alternator is and what it's SUPPOSED to be doing...

*IF*... It's an SI Series Delco, Then...
Front frame, right behind the threaded adjustment ear,

This is the NOMENCLATURE of the alternator...
In this case, top line,
61A 61 Amps maximum rated output,

Second Line,
5K10 Delco Build Number
12V 12 Volt System
NEG Negative Ground System

As stated, no issues over the past 8 years. Continues to keep the batteries
(I have 2 redtops that are swapped out every 4-5 months) charged and the juice flowing.
This is NOT the best alternator for your 'Jelly Roll' batteries.
AGM batteries ('Absorbed' or 'Activated' Glass Matt) batteries were never intended for vehicle use.

They were designed for things like 'Stand By' power and 'Battery Backups'.
Since they don't expel large quantities of explosive gas like 'Flooded' batteries do, and they can be mounted at about any angle (no liquid to spill) they excelled as 'Clean Room' battery backup batteries...

The AGM batteries like a LOW GRADE, stead charge, and a slow, shallow discharge.
Rapid charging or discharging will trap gas bubbles against the conductor plates, and cause tiny 'Dead Spots' on the plate since the trapped gas is not conductive.
Bubbles build up over time, reducing the ability of the battery to function properly.
(one reason why the companies will only give you a one year warranty on them...)

However, since the TBI conversion, the ALDL data shows 2 things that are a bit confusing:

1) After starting and allowed to idle, WinALDL is only seeing 11.8VDC at the ECM. *IF* I rev it once, the voltage will jump to 13+VDC (charging) and remain until shutdown.
Is this a product of the way it's wired?
Normal, as in it may take an off idle rev to get the alt "excited" and begin charging?
Not 'Normal', your alternator should start charging from around 800 Engine RPM...

What you are describing is the 'Excite' circuit of the alternator not working correctly.
If your engine starts and idles at a Very Low RPM
(less than 800 to 1,200 RPM)
And the alternator 'Excite' circuit isn't functioning properly, You will get EXACTLY those symptoms.

Revving up the engine will spin the rotor,
(no active electromagnet working, just what magnetism is left in the iron of the rotor)
Will eventually get the alternator charging,
At which time it will power the rotor it's self through the voltage regulator circuits.

2) During my data logging runs, there are occasional spikes to 20VDC.
These spikes only show for 1 data entry (polled every 1.2 seconds) with no ramping, increase, or decrease in voltage before/after that entry.
That's called SPIKING, and it's VERY COMMON with the SI seres alternators.

When the alternator starts making current, for a fraction of a second, the output is UNLIMITED or UNREGULATED before the regulator kicks in and controls the output.


That's why GM went to the CS series alternators in the early 80's, so they could use 'Avalanche' rectification that would stop the voltage spikes...

If you hunt up a few of my old post, you will notice that I recommend the CS series alternator for anyone going to fuel injection...

IOW, it shows say 13VDC for 20seconds, then 20VDC for 1 second, and followed by 13VDC for the next 20-30 seconds.
As best I can tell (from the data), they are completely random spikes with no regard to RPM, engine load (MAP), etc. and only show about 20 such spikes out of 8000 records (1+hour run).
What does this indicate?
Nope, it's the voltage regulator cycling, and the occasional voltage spike happens when the regulator limits current to the rotor, then a demand in the vehicle requires more current...
For an instant, the system is 'Full Field' before the regulator gets control again.

If your collection was faster, you would find a spike every time the regulator cycles.

Faulty data? (hard to believe, since the rest is dead nuts on)
Nope, your equipment is just showing you the voltage spikes that happen all the time when the regulator cycles.
Most people never see them!

Junkyard alt (or internal component) on the way south?
Sounds like the regulator 'Excite' circuit has seen better days... But that is REALLY common!
Not an issue if you don't have a computer, and you drive the vehicle regularly...

No computer means the battery works like a great big capacitor and catches the voltage spike since there isn't any super sensitive electronics on the orignal CJ's,
If you drive the vehicle regularly, the rotor will retain some residual magnetism so it will self excite at some point in the RPM range.

If you left that alternator alone for a month or two, you might have a problem getting it to start charging...
Since the residual magnetism is temporary and will dissipate to virtually nothing over time.

Personally, I think since your 'Junk Yard' alternator is on it's last legs anyway,
You should look into a NEW Junk Yard Alternator...

A Delco Remy CS 130...
VERY good low RPM charging,
Avalanche rectification so the initial start up doesn't fry things,
MUCH tighter tolerance voltage regulator intended for fuel injection,
And they grow on trees since they have been made and installed in every Small & Mid sized vehicle since '82...

A CS 130 with TWO EARS (some solid mounts have three ears) will fit right in your brackets,
You will have to use your V-belt pulley
(if you don't already have serpentine belt)
And you will need a wiring 'Pig Tail' adapter to make the CS work correctly.
That adapter is about $20 from NAPA, p/n EC82 if I remember correctly,
You will have to make your own 'Patch Cable' wiring from current wires to CS alternator plug wiring, including raising your 'Excite' wire resistor from 10 or 15 Ohms to at least 35 Ohms, and I prefer 75 Ohms to make it work for about all the CS series alternators...

Pretty Typical '3 Ear' CS 130 Alternator,


Most common type of regulator, the 'Rectangle' plug type.
There is also an OVAL type (not shown)


This shows you the positions/connections for the pins in the regulator plug connection, marked "P,L,I/F,S" on CS alternators...

'S' is 'Sense' or 'Sample', where the larger 'Red' wire from your current wiring plug hooks up,

'L' is the 'Lamp' or 'Excite' circuit, this is where the Jeep factor small 'Brown' wire connects to...

Those are the only two connections you need to hook up, besides the large battery connection on the back!

And you WILL have to add an extra resistor to this line to keep the CS charging properly.
Around 75 total Ohms is usually plenty for any version of the CS alternators.


Where to find the NOMENCLATURE on a CS alternator,
Nomenclature on a CS will be on the Front Frame, but on LONG SUPPORT FOOT MOUNT.

I smear the area with a black marker, then sand the area with something flat as a sanding block.
Brings the numbers RIGHT UP!

In this case, it looks like,
110264 80A
110264 Delco Application Number (what vehicles they went into)
80A And 80 Amps maximum

9H25 12V NEG
9H25 Delco Build Number
12V 12 Volt System,
NEG Negative ground system.

Any questions?
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