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Discussion Starter · #1 ·
A couple months ago, my original alternator died a hideous death. So I got a brand-new remanufactured one, (if that's not a contradiction), and everything was peachy until yesterday.

Driving to work, I was about to pull into Starbucks when I noticed that my Volts were dropping, fast enough that I could even see it. It was getting down near "8"... So instead of coffee and a scone I pulled into the garage next to my place of employment.

They put a gizmo on the battery leads and said, "Yup... it's not charging". I turned it off and turned the key back, and sure it enough it was pretty much just a click. They charged it up for a few hours while I was at work, and then I drove it back home; the V meter stayed around the 10 (or is it 11?) mark.

Question: does that story "prove" that the alternator is defective and should be replaced under warranty? Or is there anything else which might contribute to those conditions? I mean, the diodes are internal to the alt... I can't think of anything else besides the actual wires that could be bad. Right?
 

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Re: Alt'er Provably Dead?

Check the alternator ground. If it is broken or corroded, you get no charging.

If you have a voltmeter, you can check the voltage coming from the alternator by hooking up the positives and grounding the negative. If you have nothing coming off, the alternator is not working for some reason. You can do the same for the battery posts. If both are not within a pretty close range, you have some issues with worn or improper wiring.
 

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Re: Alt'er Provably Dead?

The engine controller controls the alternator field circuit.
A no charging issue can be caused by wiring(as already stated above) a controller issue or an alternator issue.
Post back if you need help to diagnose the issue.
 

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Discussion Starter · #4 ·
Re: Alt'er Provably Dead?

I get 14V across the battery posts.

On the four posts on the alternator, I get about 12-14 on the two top ones, and nearly zero (0.25 or less) on the bottom two. I got 12 when I put my VOM gnd on the chassis, 14 when I put it on the battery neg.

That all seems fine, doesn't it? Except that it's not my imagination, unfortunately-- the battery was dead when I pulled into the garage; the radio did shut off on that day; the dashboard V meter is down in the... I never did know how to read it-- 9 or 10 ? range. And I've got error codes I think 45 & 46, the "too much voltage", "too little voltage" ones. The too much maybe from charging, but...

So maybe the alternator is fine, but the charge is getting "lost" somewhere..??
 

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Re: Alt'er Provably Dead?

If you are reading 14 volts across the battery terminals the vehicle is charging or was when you tested it.
I would start by checking for loose/corroded connections especially if you are getting both codes(46 and 47) for charging voltage low and high.
Connect your DVOM across the battery and perform a wiggle test on all the wiring and see if you can get voltage to drop off.
There are 4 wires on the back of the alternator.
12 volt battery source
2 field wires, one should be 12 volts with the engine running and the other is field control and if you use a 12 volt test lamp connected to ground the lamp should flash on/off rapidly if the field is being controlled.
The other wire(connector) on the field wire connector is the ground.
 

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Discussion Starter · #6 ·
Re: Alt'er Provably Dead?

The wiggle test acheived nothing. I'm not surprised-- everything is tight as a kite. As far as corrosion, when I replaced the alternator I used my SOP of severely scraping the old contacts with steel wool and/or a file to make sure that fresh metal was available. So there should be no problems there.

Of the four posts on the alternator, from top, counter-clockwise to bottom, I measure 14V, 14V, ~0V, ~0V. Trying your Lamp-Test, I connected the bulb which is under the hood, (hey, it was there!), to both of the middle posts-- on the upper one, it lights up continuously; on the lower one it is dark, continuously.

But on neither of those middle posts is there any On-Off flickering like you describe. So.. the SMEC is bad..?

I want to re-iterate the following points:

1) I get 14V across the batt posts

2) The dashboard V-meter shows 9 or 10 V

3) We KNOW THAT THE DASHBOARD V-METER IS GOOD. At this point in time, it is the most reliable thing in the whole dang car. It has shown exactly 12V for the first 180k miles driven, then all of a sudden, it dropped like a rock, at the same exact time that the charging system failed miserably... It's just not a coincidence. Somehow, someway, the Volts I measure across the battery posts with my VOM is 14, but the dashboard is telling me 9 or 10, and the 9 or 10 is the real value.

????

Thanks for the help, and thanks for contributing to the site, NAJ.
 

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Re: Alt'er Provably Dead?

I sent a PM to another member who is excellant with charging systems.
In the meantime clear your fault codes, start the car and see if the code 41/47 return.
Be sure the battery is fully charged for diagnostics.
Do you have access to a scan tool?
 

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Re: Alt'er Provably Dead?

The descritions without a picture makes it hard to comprehend. So you are getting 14 at the battery running? And about 10 on the dash volt meter? I would use the volt meter to check voltage at the fuse box to back up the dash gauge. Does the car have aftermarket replacement battery cable ends? If so take them apart and clean the wires and check the bottom side of the metal strap that clamps the wires down to the lead base. I have seen alot over the last few year rust and cause issuses.
Tim
 

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Re: Alt'er Provably Dead?

Let me know if you need the charging system wiring posted.
 

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Discussion Starter · #10 ·
Re: Alt'er Provably Dead?

The descritions without a picture makes it hard to comprehend.
Ok, well I can take a pic of anything you like. To get us all on the same page, here is what I'm talking about:



...and...



>So you are getting 14 at the battery running? And about 10 on the dash volt meter?

YES! I know that sounds bizarre, but that's the truth.

>I would use the volt meter to check voltage at the fuse box to back up the dash gauge.

What points in the fuse box can I measure to be helpful?

>Does the car have aftermarket replacement battery cable ends? If so take them apart and clean the wires and check the bottom side of the metal strap that clamps the wires down to the lead base. I have seen alot over the last few year rust and cause issuses.

No, no aftermarket. And no rust in the e compartment; nice post connections, with dielectric grease goo. But I'll certainly look around if you can explain "the metal strap that clamps the wires"...? Wha..?

When NAJ said "clear the codes"... it always makes me think that there's a clever way to do this. I know of no way other than disconnecting the battery... If there's another way, please let me know!!

Anyway, I disconnected the batt; reconnected; ran the engine for maybe two minutes, (I'm running on batt, remember!), and then checked codes.

I now have only code 12, which is "some idiot disconnected the battery"...
 

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Re: Alt'er Provably Dead?

ok if you have 14 at stud A and at the battery you are charging. You can check voltage at any fuse in the box. I myself you check at least half of them since the fuse box usually has more then one feed. If you get 14 at the box my best guess is the cluster has an issue. Disconnectiong the battery to clear codes is fine. even with a scanner 12 shows up.

What codes were stored to start with?

Your alternator is not the usual one seen here. most are either old mopar units or newer denso units. I would guess that might be a bosch unit. Terminal B and C in your diagram are the 2 field wires. They are the ones the computer uses to control the output voltage.

In your picture it looks like the mount has bushings. Is the ground from the alternator to block good. Use your volt meter to check it both off and running. hook the postive meter lead to the batteries positive terminal and use the negitive lead to get readings at the battery engine block and alternator case and post those numbers back.

clusters are known to have solder joint issues. So check the voltage at the fuse box and post back. 14 volts running is good. what is the voltage at the battery with the engine off?
Tim
 

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Discussion Starter · #13 ·
Re: Alt'er Provably Dead?

What codes were stored to start with?
Numerically, I don't quite remember: 45 & 46 ? But they translated to "Too Much Voltage" & "Too Little Voltage". ( And I'm speaking of when I read the codes after driving home from the garage, on the fateful day ).

Ok-- I tried to measure everything you asked for, except that I failed at the fuse box: I didn't think that it would be so dark in there-- I can't see a damn thing, so I'll have to figure something out, or update this post when I have time on a non-working day. But here's the rest of it:

Between the battery posts:

Eng on: 13v90
Eng off: 14v04


Between Pos battery terminal and Post D on the alt'or:

Eng on: 13v92
Eng off: 14v01


Between Pos battery terminal and casing of alt'or:

Eng on: 13v99
Eng off: 14v07


Between Pos battery terminal and braided gnd cable from block to firewall:

Eng on: 13v99
Eng off: 14v07


I will try to get readings from the fuse box for you asap. I might have to set fire to the seat...
 

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Re: Alt'er Provably Dead?

Doubting the accuracy of your DVOM....
14 volts with engine off ?
That would be normal charging voltage with the engine running.
Your vehicles voltmeter is probably correct and the vehicle is not charging.
 

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Re: Alt'er Provably Dead?

I would have to agree on checking the volt meters accuracy.

Normal fully charged battery reading with engine off should be around 12.5 volt. A system that is charging should be at least one volt higher. So around 13.5 minimun. A normal range for a computer controlled mopar would be in the range of 13.6 to 14.6 depending on battery temp.

Your numbers are almost the same on and off higher while off this is seem when a system is not charging. What type of meter are you using?
Tim
 

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Discussion Starter · #16 ·
Re: Alt'er Provably Dead?

What type of meter are you using?
One with an almost dead battery, that's what type!!

:eek:

Heh. Sorry, guys. Good catch!


Ok, with a *fresh* battery in my VOM, I get:

Battery posts, engine on: 11v86
Battery posts, engine off: 12v09

Engine on, between Post A on alt'or and Neg Battery: 11v81

Engine on, between Post B on alt'or and Neg Battery: 11v64

I cut power and measured a second time; the numbers were all within a percent of a volt between tests.

The V meter in the dash is still substantially lower than what my VOM measures, however; it's dropped a bit lower than the picture above, of course. And I believe it-- when I started up the car to do these tests, the engine sounded "funny". I can't explain it, but it wasn't my normal engine.

Anyway, I think you will tell me that I'm not charging... Now what?
 

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Re: Alt'er Provably Dead?

ok now those numbers look more like numbers for having dead batteries. Do a volt reading across the field wires. pos on B neg on C. That reading will tell me if it an alternator or control issue.
Tim
 

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Re: Alt'er Provably Dead?

if you are getting battery voltage across terminals b and c the field control is working and the alternator field is open. You can back up that by removing the wires and ohm b and c should be in the 2.5 ohm range. My guess is its a bit higher or open.

The denso alternator is the best unit out there. As UnaClocker stated replace with one of them. I was never sure if they all mounted the same I know as time moved into the 90's mounts were the same.
Tim
 

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Discussion Starter · #20 ·
Re: Alt'er Provably Dead?

You can back up that by removing the wires and ohm b and c should be in the 2.5 ohm range. My guess is its a bit higher or open
Ok, I removed the cable and measured between B and C, and it reads completely open. ( Verified my VOM both before and after by measuring 1% resistors, from 10ohms to 100k... )

So-- everyone is now confident that the alternator is defective, right? I'll try to get the one you guys are recommending, but my first priority is to be sure I'm right when I ask for my money back on this one!
 
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