Alternator?

Alternator?
If your voltage is going from 12 to 18, the regulator most likely is bad.
 
With SI & CS series, If the case 'Ground' is bad, the voltage will spike and wonder around.

DEDICATED GROUND WIRE.

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When changing from SI to CS alternator, you MUST use a 35 to 150 Ohm resistor in the 'Excite' terminal (Idiot Light) circuit or it will NOT regulate correctly.

I usually use a 75 Ohm 1/2 Watt resistor and things work fine after that.
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Also, some versions of the CS series alternator are voltage controlled by the ENGINE COMPUTER.
What version of the CS alternator did you use? What vehicle was it intended for?
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DID YOU ADD A RESISTOR, EITHER IN AN 'ADAPTER' OR BY HAND TO YOUR HARNESS?
 
My reasoning behind the regulator was assuming you have added a resistor and also have a good ground. Since you said you rewired it completely I assumed you did that, if you didn't just do what Team Rush said and then report back...

Good catch TR!
 
I've done a bunch of these 'Diagnosis' things, over 20 years owning my own shop, and 10 years with a starter and alternator rebuild shop...

One thing you learn quickly,
You NEVER get the FULL STORY,
You NEVER get the TRUE STORY,
And when you are doing customer service on the phone, EVERYONE lies to you for the first 30 minutes...

Since I am coming into this late, and I have No Idea of this guys abilities, I figure I'd better start from scratch and see how much he know and what he did before I start asking questions...

'Full Install' or 'Full Rewire' for me or you might be different for someone else...
Since the idea of a dedicated ground wire seems alien to most guys, I though I'd ask...

Same with the needed resistor.
If you don't put in the resistor and you install a CS series alternator, these are EXACTLY the symptoms you will get...
That's why I asked about the resistor SPECIFICALLY...
(and once the regulator is damaged, adding the resistor afterwards won't help... I've tried!)

NAPA sells an 'Adapter' for about $25 that has both plugs (SI on one end, CS on the other) and it has the required resistor built in,
But if the guy didn't use a 'Pre Made Adapter', then WE NEED TO KNOW IF THERE IS A RESISTOR IN PLACE!
---------------------------------

One other thing that comes to mind,
Jeep Volt gauges are just CRAZY sometimes!
I try to tell people to take voltage with voltmeter at the battery or cigarette lighter or somewhere, and don't trust the Jeep volt gauge until you can prove it's correctly reading the 'Surges' and 'Drop-outs'!
 
Alright, I rewired it as in removed all the old :dung: wiring.
I used a dedicated ground first to the battery.
A new cable from the batt terminal to the battery side of the starter solenoid with a fuseable link.
A new white wire with a resistor and LED idiot light.
A new red wire that goes to a fused hot wire under the dash also with a fuseable link or fuse wire what ever you want to call it

Other than the LED idiot light everthing is hooked up like diagrams I've seen on the net.

At this time there is a NEW stock jeep alternator in it.

I get 12+v while idleing when the idiot light is on using a voltmeter, measured at the batt. and at the alt. When the idiot light is off and the jeep volt guage is over around 16 -18v I haven't had a chance to measure it at the battery or alt. It's always on the way to work or pitch black dark outside.

But having the idiot light stay on or off during a ride and watching the jeep volt gauge go from around 12 to around 18 tells me somethign isn't right.

I used proper soldering techniques and used the matte finish heat shrink on all connections.
 
BrockGrimes said:
Alright, I rewired it as in removed all the old :dung: wiring.
I used a dedicated ground first to the battery.
Click to expand...

VERY GOOD! Most guys don't do that, and wind up with charging problems in short order!

A new cable from the {ALTERNATOR} batt terminal to the battery {CABLE} side of the starter solenoid with a fuseable link.
Click to expand...
Again, EXACTLY CORRECT!

A new white wire with a resistor and LED idiot light.
Click to expand...
Now. WHAT SIZE RESISTOR?

Normally, LED Lights won't work as 'Idiot Lights' since they don't pass enough current to work as 'EXCITE' sources.
You usually have to use a regular incandescent bulbs for 'Idiot' lights.
There are exceptions, but they are RARE!
------------------------------

A new red wire that goes to a fused hot wire under the dash also with a fuseable link or fuse wire what ever you want to call it
Click to expand...
That would be the 'Sense' or 'Sample' wire.
Normally, you don't hook it up under the dash unless you are having charging problems to start with...
Big lights, big stereo, stuff like that causing problems...
------------------------------------

Other than the LED idiot light everthing is hooked up like diagrams I've seen on the net.
Click to expand...
LED's have a very specific polarity, and not all of them hook up the direction you want to go with the power (out to the alternator),
Also, most of the smaller LEDs don't pass enough current to 'Excite' the alternator...

Like I said, there are exceptions, but LEDs that are robust enough to work as 'Idiot' lights are RARE (and usually expensive).
-----------------------------------------------

At this time there is a NEW stock jeep alternator in it.
Click to expand...
'Stock Jeep' means an Delco SI series alternator, so the resistor isn't a big woop... but they take more power to 'Exicte' than the CS seires, so a LED 'Idiot' light might be the restriction in the line that's causing problems...
------------------------------------------------

I get 12+v while idleing when the idiot light is on using a voltmeter,
measured at the batt.
Click to expand...
So you aren't relying on Jeep Volt gauge for readings!
GOOD! I believe the DVM over the gauge,
AND,
It's verification of the gauge...
--------------------

...and at the alt. When the idiot light is off and the jeep volt guage is over around 16 -18v I haven't had a chance to measure it at the battery or alt. It's always on the way to work or pitch black dark outside.
Click to expand...
Just for testing purposes...
Do this,

Connect the 'Smaller Red' or 'Sense' wire to the starter relay battery terminal side...
And take the LED out of the circuit.

Taking the led out can be as easy as using a Jumper Wire from one leg of the LED to the other...
Just let the 10 or 15 Ohm resistor work the way it's intended to...

Call this a 'Test Configuration'.... And see what you get.
----------------------------------

But having the idiot light stay on or off during a ride and watching the jeep volt gauge go from around 12 to around 18 tells me somethign isn't right.
Click to expand...
When you choke the input for the 'Excite' wire down to where it's not working, the alternator will eventually start charging on the residual magnetism in the rotor...
The voltage will flash WAY UP HIGH, then the regulator will catch it and shut things down...

And the cycle starts over again!

You have to rev the engine up, get the alternator spinning faster than 'Idle Speed' to make that happen, so that's why it happens when driving...

Try taking the diode 'Idiot Light' out of the circuit and see if that stops the problem...
---------------------------------------

I used proper soldering techniques and used the matte finish heat shrink on all connections.
Click to expand...

Excellent! Glad to hear someone is doing things correctly!
I think the LED light is your problem, and you may now have a problem with the regulator since you voltage flashed well above the usual limits of the regulator...

But take the LED light out of the circuit and see if that takes care of the problem!
Let us know what you find out!
 
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I have a 100ohm resistor as that was what was most mentioned being used, but did read 35 ohm was acceptable.
The LED i picked up from radioshack, it's a all in one setup the bulb and resistor are in a houseing, and is rated for 12v. I'm wondering if the 2 resistors are to much for the stock alternator.
I'll remove the LED from the setup and see what I get, I had bought a regular bulb type idiot light just in case the LED didn't work out.

I'll let you know I'll make the change and post back up later today.
 
Well I replaced the LED with a regular light, no change the light stayed on and voltage was around 12. I then moved the red wire from the 12v source in the dash to the battery post on the alt. and the light went out and the dash gauge reads 14v+-. Guess it was the source under the dash giving me :dung:.
 
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Yeah it's been a PITA, I wanted to set it up right but it didn't like that conenction for some reason. So now it's set up like it originally was but now I have an idiot light, and good grounds, so all is good.

Now on to the Taurus fan install, geez, I gota find a buddy who likes electrical :dung:.
Give me wrench turning nastyness anyday.
 
Well after reading thru the painfully complete directions/troubleshooting discussed here, I need to re-think the way my prototype dash is set up. Right now I have LEDs for all the warning lights, working with the full guages. So, since I want all the warning lights to match, I have to go with regular incandencent bulbs in all of them. :(

Good thing I found this out before I ruined another sheet of $23 diamond plate!
 
mylittlecj5 said:
Well after reading thru the painfully complete directions/troubleshooting discussed here, I need to re-think the way my prototype dash is set up. Right now I have LEDs for all the warning lights, working with the full guages. So, since I want all the warning lights to match, I have to go with regular incandencent bulbs in all of them. :(

Good thing I found this out before I ruined another sheet of $23 diamond plate!
Click to expand...

HOLD UP!
If jumping the LED fixes your problem, I can figure out a way to make the LED work...!
We do it for street rods all the time!
 
TeamRush said:
HOLD UP!
If jumping the LED fixes your problem, I can figure out a way to make the LED work...!
We do it for street rods all the time!
Click to expand...


fortunately, I don't have the problems the OP has yet. All my pretty new guages are sitting in my spare room layed out on a table as I try to get the dash design right.

So spill it...whats the trick to make the LEDs work? :notworthy:
 
mylittlecj5, the LED is only a problem when using it as an idiot (warning) light for the alternator (as they do not load the sensing circuit correctly). When using them as warning lights for the other gauging (like an oil pressure switch) you don't have to worry about what was done for the alternator wiring, you most likely will not have any problems as the switches are mechanical and simply close a circuit.

This problem has nothing to do with a warning light for any other gauging except for a warning light for a SI alternator.
 
CJ said:
mylittlecj5, the LED is only a problem when using it as an idiot (warning) light for the alternator (as they do not load the sensing circuit correctly). When using them as warning lights for the other gauging (like an oil pressure switch) you don't have to worry about what was done for the alternator wiring, you most likely will not have any problems as the switches are mechanical and simply close a circuit.

This problem has nothing to do with a warning light for any other gauging except for a warning light for a SI alternator.
Click to expand...


Gotcha, but with the custom dash I'm working on, ALL the warning lights are matching LEDs, including the voltage...I just want them all to match.

If I have really have to, I will change them all to incandescent but thats a last resort...
 
No problem, how about posting an intended wiring diagram in your dash thread and we can tweak it to work with what you have. That way we don't clutter up this thread with some off topic banter. :)
 
Hmm OK but I havent got that far yet...:)
 
mylittlecj5 said:
Hmm OK but I havent got that far yet...:)
Click to expand...

Nothing to it really...
Just use a resistor in line for the load to the 'Excite' terminal (takes the place of a 'Light Bulb'), then jump your LED and it's resistor OVER the resistor.

LED will still work like an 'Idiot' light since BOTH sides of the LED will have positive current when the alternator is charging, the light will go out...

But the larger 15 to 75 Ohm, 1/2 watt resistor will do the real work passing current to the 'Excite' terminal...
(15 Ohm for SI alternators and Ford alternators, 75 Ohm for CS series alternators)
 
That seems easy enough..thanks TR
 
I had a resistor in my line plus the LED and it's resistor, when I swapped out to a regular bulb it didn't fix the problem. Moving the red wire from the source under the dash back to the batt terminal on the alt. is what fixed it.
I think the all in one LED (housing, resistor, LED) rated for 12v I got at radio shack with the resistor I added to the line will work, now that I figured out what the issue was.

If I'm inclined to stand on my head again I'll swap the LED back in and see how it does.
I've also wired my entire dash for LED's, BTW.

Don't ask for a diagram as my under dash wiring was hacked by a PO and I had to clean up and replace stuff.
But it wasn't hard, you can buy premade LEDs with resistors or wire up your own. I did the latter.
 
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