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#177234 10/09/09 03:35 AM
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Am asking this in desperation, as I know there are alot of bright minds here, before I have to go to the shop and get soaked for labor costs.

The alternator in my 96 Ram pickup fried out, so I replaced it.
Easy fix.
Now theres no charge getting through to the batt.
Changed the 120 amp alt fuse, no joy.
Took the new alt back out to have it bench tested, passed 3 times. Batt is a brand new Diehard gold which holds a charge just fine.
Looked for any fusible links or frayed wires between the alt and batt, didn't find any.
Connections on alt all tight & solid, no way I could botvh them, they only hook up 1 way.
Can anyone thing of what may be stopping the charge from reaching the batt ?


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Did you put the belt on?

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Do you have a voltmeter? start car up. What reading at posts of battery terminal when cables attached?

Now remove the positive cable and take a reading.

IMO, you may have fried your battery.

Will the car stay running with positive cable removed?


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Reads a bit under 12v running.
don't think the batt is fried.
* It takes and holds a charge just fine with a charger
* truck cranks right up, something it would not do on a weak batt, not to mention a dead one
* I've driven a few miles on just batt power

I'll try the pos cable thing tomorrow, thanks - And yeah FB, belt is on.
Would be nice if it was a dumb error like that.


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Just off the top of my head... use voltmeter to test the battery without cables attached. Record voltage. Connect the battery cables and start up car. Check voltage of battery while car is running. Should see a rise in voltage. While car is running, (with a thick heavy glove on your hand), disconnect battery... does car continue to run or does it stop instantly?

Once upon a time, Chilton had in the front of their manuals a fairly straight forward diagnostic chart. Look through it and go step by step.

Theres really not much in the charging system..... battery, regulator, alternator, link, cables, ignition switch, starter..

Heres a chart:

http://www.google.com/imgres?imgurl=http://www.sundevilauto.com/images/diagrams/charging-system.jpg&imgrefurl=http://www.sundevilauto.com/auto-diagrams-charging-system.asp&h=512&w=700&sz=457&tbnid=loNpESka7E07xM:&tbnh=102&tbnw=140&prev=/images%3Fq%3Dcharging%2Bsystem%2Bdiagram&hl=en&usg=__IEvkgIpwFc_dd3fPQto7s5KYcd4=&ei=JDPPSvjeGdLL8QbFz8HsAw&sa=X&oi=image_result&resnum=2&ct=image&ved=0CA0Q9QEwAQ

I had an 67 Mustang that used to constantly kill batteries. I changed out the battery, alternator, cables, ...till I got to the regulator. That was my cause. But go throught the Chiltons diagnostic step by step and see what you find..


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Have you checked voltage at the alternator yet?

What engine is in it, 2 or 4 wheel drive?

I can check bulletins for you from the manufacturer.


-Jeff

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Haven't done the cable disconnect, the alt has been professionally bench tested multiple times, its good.
You are correct, theres not much in the charging system, but when power isn't making it from point A to point B, it can be a challenge tracking down the culprit, especially without decent schematics.
I have a Haynes, doesn't have much at all about diagnosing problems.
In fact, if I went only on what the book said, I would have declared my alt a dud, as the only testing procedure was measuring output at the battery - That tells you if you have low output or not, true ,,, But doesn't take into account that the problem might be in the wiring.
Regulators are built into most modern alternators and thus aren't easily serviceable.

Dr, the alt was professionally bench tested and passed with flying colors.
Its 2wd, I'm a member of a 2nd gen Ram forum, haven't got much help there.

My Haynes does say theres a fusible link between alt & starter, I have yet to find it.


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Let me ask. Did you remove any of the computer/pcm connections while the battery was connected and or key was on?

According to my information, this system controls voltage to the battery through the PCM. Found a bulletin related to a "no charge" condition.


-Jeff

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Nope, I did do one dumb thing that probably caused this.

When I removed the failed alt, I of course disconnected the batt.
As I don't like leaving my truck without the alarm on, I reconnected the batt after I was done, making sure no lose wires were grounding.
So the next day when I had the new alt, it turned out they gave me the wrong one, they matched up exactly, but the top bolt would not go through the alt.
No big deal, too late to get another one, I had some other things to do under the hood but the [censored] alarm kept setting off, so in order to turn it off you have to put the key in accessory position and hold a button for 5 seconds, I did that and it didn't turn off, like a moron I mistakenly turned it in start position - And this, of course, with no alt installed.

I heard a little click, lost all power for about a minute, I took the battery cable off and put it back on, and power was back.
But I think whatever that little popping sound was, must be the root of my problems.
Its not a fuse, I sure wish it was.


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Hard to say what happened now without looking at it. But I fear you may have fried the charging circuit in the PCM. Chrysler computers are very sensitive.

The only other thing I can think of off hand, is that you reversed the "Gen field driver" and "ASD relay output" connections on the alternator harness.

If you do take it to the Dealer or other shop, tell them what you told us...It may help avoid the additional aggravation charge that shops add on when figure out there was operator error involved.


-Jeff

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Well, one would think thats why fuses were invented.
Don't you think it would throw a code if that was the case ?

No chance of reversed connections, the way the wires are, it is physically impossible to make a wrong connection ie:wires are of a certain length & position, and will only reach/fit to the areas of the ALT which they belong.

I know the connections you are referring to, those in particular would be impossible to reverse, even if you wanted to, without cutting/splicing wires.

I know everyone makes mistakes, I am rather meticulous though, and if I botched a simple operation like that, I would have no business even opening up the hood in the 1st place.

Well thanks for the help guys, didn't get a chance to mess with it today, looks like I'll have to have it diagnosed at a shop.
new-2.jpg

Last edited by Xray; 10/09/09 09:14 PM.

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Found out it is the voltage regulator, which is a function of the PCM.
Rather than get a new computer, I'm going to bypass it and install a generic VR from, say, an 1989 Dakota or something.

Will probably leave the GEN light stuck on, so long as I'm getting 14v at the battery, I can live with that.



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