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Confirm an alternator conclusion?

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Category: The Garage
Forum Name: Electrical - non engine
Forum Description: Charging systems, lights, non-ignition system, it goes here.
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Topic: Confirm an alternator conclusion?
Posted By: kensamc
Subject: Confirm an alternator conclusion?
Date Posted: Nov/17/2009 at 2:21pm

 This one is for my 86 Grand W with the 360 .
IFSJA had several posts about charging gremlins.... followed everything to the letter and just last night
got stranded with my 2 year old on board.

 They conclude that the fusible link is the weak link, BUT I had the prescribed jumper wire running from alternator to the positive post side of the solenoid on the fender.

 No shorts show by metering from positive to block with the neg terminal disconnected.

If I disconnect the positive terminal with the engine running the alternator meters 15 volts.
Once reconnected to the battery, it meters anywhere from 11.73 to 12.52 volts ... never higher.

Already new battery, new alternator(rebuilt) and the jumper wire around the fusible link.

This has to be an intermittent alternator, right ??

If I have to take the wife's car to work, she'll never let me forget it.....




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1986 Jeep Corp Grand Wagoneer




Replies:
Posted By: billd
Date Posted: Nov/17/2009 at 2:39pm
Depending on exactly what you disconnected and when and run it, if there wasn't something amiss before, good chance there is now.
One should never run with anything disconnected, regardless of what you read on the self-help sites.
Diodes and regulators can be blown that way.........
Rebuilt alternator doesn't necessarily mean good..........
With the engine NOT running, what is battery voltage?
With the engine RUNNING and everything connected, what is the voltage at the battery?
GM alternators have a tab you can short to bypass the regulator (assuming GM alternator here) what do you get if you short that tab?
Ignore ANY advice on disconnecting wires and running it with things disconnected.................. and NEVER disconnect anything with the engine running......


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Posted By: kensamc
Date Posted: Nov/17/2009 at 2:49pm
Bill

Aside from fear of frying myself, I worried about disconnecting it for the alternator's sake as well, but was at my wits end. It is a 10si .... knew nothing of a tab to short on that ...
This is my third battery since replacing the alternator. Now that it has been run down once, it metered 11.73 when I limped home.
 Also what it metered this morning after sitting all night.
With the engine running and everything hooked up, this morning it read 12.23

The check for short was of course, with the engine off. Checked both between pos and block
and between positive cable and battery terminal. 

I half assumed I may have lost the alternator when the last battery died, because I understand it is not the alternators job to fully charge a dead battery, but I managed a quick jumpstart and it metered 12.9 volts, and off I went.
 
 11.73 is too low for the battery I know... 2 week old Diehard too

Thanks for the prompt reply BTW



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1986 Jeep Corp Grand Wagoneer



Posted By: kensamc
Date Posted: Nov/17/2009 at 2:50pm
 Not that it makes it a lot better to do, but my Dad was a car guy and a brilliant diagnostician .. wish he was still around...
And some of my bad troubleshooting habits came from the family tree ....


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1986 Jeep Corp Grand Wagoneer



Posted By: billd
Date Posted: Nov/17/2009 at 9:49pm
The problem is that some old-skool troubleshooting came from the older technology - generators and alternators with dual circiuit regulators - cutout relays, etc.
Check out this image - there's a D-shaped hole. Inside that hole is a tab. Put a small screwdriver in there and ground the tab to "full-field" the alternator (touch tab and alternator case at same time) - it should hike the voltage up to 15-16volts. Don't hold it there and don't run lights or radio, etc. while doing this.  If it doesn't whine and start charging heavy, there's an alternator issue. If it does, a regulator issue (or wiring issue).


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Posted By: kensamc
Date Posted: Nov/18/2009 at 8:22am
 I can try that, though the alternator is awfully close to the exhaust... have a few burns to prove it so far ...
 Does the fact that it went to 15 volts plus when disconnected from positive imply a problem already ?

The info on IFSJA made sense after all I went through ; but having bypassed (actually augmented) the fusible link already there isn't much left but the alternator itself....
As you said, rebuilt doesn't mean good...


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1986 Jeep Corp Grand Wagoneer



Posted By: rockrash
Date Posted: Dec/26/2009 at 8:28am
A delco alternator can be pulled down by a short or poor ground in the system. Has your amp/voltage meter been jumping around on rough roads or perhaps when you put on your turn signals???  Check for loose or hanging wires....especially any butt splices that can have weight pulling on them. A wire that looks fine with a connector inline can cause the fault that you mention. Any local parts house can usually test your alternator....many go through a detailed test of diodes, regulator etc.
Pull it and have it tested.....but on a vehicle that old, chances are it is a wiring issue.
I have an ol' Blazer that gave me the same fits till i began securing wires and sealing connections. After that was done it seldom sees lower than 14v running lights, heat, and wipers.
Good luck.


Posted By: kensamc
Date Posted: Jan/05/2010 at 1:50pm
 AFter all the hunting and goofing, it proved to be the regulator in the alternator.
I did upgrade to the Powermaster 140 amp AND ran the secondary charging line as detailed on IFSJA.
First time since I have owned the GW that it showed anything north of 13v on the voltmeter in the cab, and it meters at the battery at a beautiful 14.2.

 I honestly don't know, but assume that AMC cars used the same alternator at the end of their days ????
But probably not the fusible link....

Did or did not, I can say that a bigger , better alternator and the secondary charging line is a must for the late model Grand Wagoneers.

Thanks all for kicking this around



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1986 Jeep Corp Grand Wagoneer



Posted By: billd
Date Posted: Jan/05/2010 at 2:18pm
AMC used Delco in the 80's, although they used others as well.
Depends on the options and if it was considered "heavy-duty" or not.
Both of my Eagles, with A/C and all the trimmings, have Delco alternators factory on them.
(and I'll rebuild them as well)
The Jav will forever be Motorola, or at least as long as I own it.


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Posted By: poormansMACHINE
Date Posted: Jan/05/2010 at 7:12pm
Originally posted by kensamc kensamc wrote:

But probably not the fusible link....



A fuse of some sort should be present be it a fusible link or a physical fuse.


Posted By: kensamc
Date Posted: Jan/06/2010 at 9:58am

  MACHINE

 Didn't mention it, but do have a marine grade 150 amp thermal breaker in line with 10 gauge wire
for the secondary charging line. Detailed on IFSJA, and searching for the breaker found it as cheap
as 20 bucks and as high as 50 ..... 
 It NOT working any better with this installed at first helped me narrow it down to the regulator ...
With the new alternator and this line in, had 13v at very first moment it started, and 14+ within just a few seconds.

 If anyone is on the same boat with an FSJ, team grand wagoneer sells a 106 amp ....ready to put in.
The powermaster is the same money, 140 amps, but will need to be reclocked 180 degrees and the alt output post is bigger than the stock alternator, so you will HAVE TO make the other charging line or splice a bigger spade onto the existing fusible link.

 The only thing that presents any noticeable draw to my rig now is the power windows and I am installing an OEM NOS drivers door switch and harness from TGW this weekend and cleaning and lubing all tracks and connections to hopefully fix that. But heater, lights, foglights, all show no drain on the in cab voltmeter.


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1986 Jeep Corp Grand Wagoneer



Posted By: billd
Date Posted: Jan/06/2010 at 11:05am
You are doing all this because you are concerned the meter is showing a draw when you use something?
Wow. Not sure where the logic comes from, I guess...........
The EEs here can correct me if I'm wrong - but that's not the way these things were originally engineered, and sure seems like a total waste, because, in reality, you aren't gaining anything in efficiency, etc.
What in the world is in that Jeep to require all this?
Must have a LOT of really heavy electrical equipment running all the time.
And IMO, no offense, but "so what" if you show a bit of a draw when running the windows up and down?
Does this mean that if you ran a business, and you had slow days that 2 folks could keep up with, typical days that 4 people could deal with, and busy days but once a month that it took 10 people to keep up with, you'd keep 10 people on full time so the staff would never have to work hard?


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Posted By: ramblinfsj
Date Posted: Jan/06/2010 at 11:25am
Glad you got it figured out. With the engine running, a volt meter should read 14 volts at the battery terminals to show a good working alternator but I guess you know that know. Sorry I didn't see this thread earlier or I would have saved you some time.

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1982 Jeep J-20
1965 Rambler American 220
1978 Jeep Cherokee w/401
1983 Jeep J-10
1979 Concord DL 2dr


Posted By: billd
Date Posted: Jan/06/2010 at 11:32am
And do NOT worry if it's under 14v. Specs for different batteries and different temps and charge states will vary. 13.5 is still just fine and in specs for most batteries. So if it's UNDER 14 or runs in the mid-13s you don't necessarily have anything at all wrong.
On a very cold day, it might hit say 14.7, then drop to 13.7 as it warms up - normal.  Cold batteries require more voltage to charge. And different battery technologies and different ages also might give you different needs for voltage/charge.  I think folks get too hung up on a set number.
I can show you GM specs that cover a range of nearly 2 volts!
12.6 is normal for a charged battery with nothing running and no load. Each cell is 2.1 volts.


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Posted By: gwryder
Date Posted: Jan/06/2010 at 11:33am

Disconnecting the positive cable from the battery makes the voltage regulator think the battery is fully charged. A fully charged battery has an effective resistance of ~1 Ohm. This is all Ohms law, Voltage= Current x Resistance. With the battery cable off, the resistance is extremely high, so the alternator puts out very little current. With the higher voltage the regulator cuts off charging current. It gets a little more complicated, but this is the basics.  When the battery is hooked up, the voltage drops because of battery loading the alternator. The state of charge of the battery determines the effective resistance the regulator sees and thus the system voltage.

Run the engine @ 2000 rpm and monitor the battery voltage. It should increase over a little time to ~14 volts. This will tell you the regulator and alternator are working. A good tool to have with these types of problems is a Inductive Current meter. All you need to do is clamp the pickup over the battery cable or alternator output cable and read the current. One can use the Inductive current meter to monitor the output of the alternator when full fielded. That will tell quite a story.

It's really important for all the connection to be clean and tight, else a voltage drop will occur. The voltage drop fools the regulator into thinking the battery is charged, because the drop adds resistance to what the regulator sees. Because the effective resistance of the battery is very small, any added resistance makes the battery appear to the regulator to be charged. Anyway, I think the alternator is Ok.


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John
70 AMX





Posted By: billd
Date Posted: Jan/06/2010 at 11:54am
PLEASE! DO NOT EVER EVER DO THAT!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
Never remove any battery cable with the alternator charging! Good way to blow things!
The modern electronic regulator does not sense in any way resistance. It can't sense load, resistance, amperage, etc. Only voltage.
And no, another reason it's not a good test is that the regulator will actually in some cases self-destruct. That's because it will not see voltage and will keep stepping it up (depending on where it's sensing from) and can get, in the case of Motorolas, enough voltage in the aux terminal to fry the regulator - it will go into an endless loop and just keep building.
Motorola is VERY specific about all this in their technical manuals (as is GM)
Never full-field a running Motorola either. You'll pop diodes and possibly destroy the regulator. It should be connected and disconnected when OFF, or better yet, use a field rheostat.
Removing a cable is a bad method that results in more damage than anything in many cases.
Can't tell you how many bad diodes I've replaced....................
My theory is that all this is a carry-over from the old generator and manual/mechanical regulator era.
Anyone that removes a cable from a running alternator, I simply can't guarantee that alternator.
Best test - LOAD the system. Carbon pile across the battery will drop voltage and cause the regulator to try to keep the voltage up to spec. More load or draw, the more field current the regulator will supply in an attempt to keep the voltage up to what the regulator believes it should be. Of course, you can then measure the amp output.
You can actually test an alternator output in other ways - turn on the heater blower, all lights on high-beam, radio, etc. In addition, disconnect the coil primary and crank the engine for a while to help drain the battery. Then start it and turn everything on.
You can get a good idea of the alternator/regulator condition that way.
Although the cheap magnetic amp meters work ok, the best is still an in-line meter, usually put in place with a disconnect switch on one battery post.



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Posted By: kensamc
Date Posted: Jan/06/2010 at 12:01pm

 Bill

No, I didn't do all this because the meter moved. I did all this because I ate 3 batteries and 2 alternators
and it was you that first said a "new" alternator doesn't mean a good one and you were right in the end.
But I still think the fusible link may have played a part in wasting the first 2 batteries, one of which was before the bad-from-the-parts-store  alternator.

 I expect accessories to draw, and only mentioned the times it does move in support of it's otherwise "flawless" performance.
 The truck is bone stock with no extra electrical accessories... hell, the radio doesn't even work .....
but it does have power everything, AC , rear defrost, fog lights and factory installed trailer hitch and harness, which I use.

 I only learned of the secondary charging line while trying to suss this, and thought it seemed a good idea and a good enough idea to share with anyone else stuck in a late model FSJ charging conundrum.

 I might have done the CS alternator upgrade if I hadn't found the IFSJA post and the Powermaster unit first. As this is my Chicago weather, daily driver, low charging is not an option.  98 amps seemed only passable, 106 sounded better, and the 140 amp was the same money. 

 I am perfectly happy with where it is now. The window maintenance has to be done because the truck is 24 yo and has 140k on the clock. If when it's all lubed and happy, it shows under 13v while I roll down the windows, I will still smile and drive off, knowing my battery is charging....
 I don't expect 14+ volts all the time. I'm just glad I got through 2 weeks of charging my battery overnight to drive to work the next day .....






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1986 Jeep Corp Grand Wagoneer



Posted By: billd
Date Posted: Jan/06/2010 at 12:17pm
Most of all, enjoy that Jeep!
Regardless of charging systems and batteries, there's a 110% chance the windows need some servicing anyway - hardened lube/grease, dirt, old connections.
Just would be a good thing to do just because.
My ambo wagon had a bad regulator - I was in college and didn't have extra funds, but had an old battery charger and an outlet right outside my apartment.
I found out that car could get me back and forth between Ankeny and south Des Moines 2 days, including the after-dark 10:30pm drive back to ankeny WITH headlights on before needing a recharge. Got by for a couple of weeks and finally saved the $ for a regulator.
That wagon was power-everything windows, etc. and the drive to work was 30 minutes each way.
That's an hour each day with half of that time with lights, defrost, etc. on.
That little 343 never missed a beat, though.


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Posted By: purple72Gremlin
Date Posted: Jan/06/2010 at 12:23pm
Originally posted by gwryder gwryder wrote:

Disconnecting the positive cable from the battery makes the voltage regulator think the battery is fully charged. A fully charged battery has an effective resistance of ~1 Ohm. This is all Ohms law, Voltage= Current x Resistance. With the battery cable off, the resistance is extremely high, so the alternator puts out very little current. With the higher voltage the regulator cuts off charging current. It gets a little more complicated, but this is the basics.  When the battery is hooked up, the voltage drops because of battery loading the alternator. The state of charge of the battery determines the effective resistance the regulator sees and thus the system voltage.

Run the engine @ 2000 rpm and monitor the battery voltage. It should increase over a little time to ~14 volts. This will tell you the regulator and alternator are working. A good tool to have with these types of problems is a Inductive Current meter. All you need to do is clamp the pickup over the battery cable or alternator output cable and read the current. One can use the Inductive current meter to monitor the output of the alternator when full fielded. That will tell quite a story.

It's really important for all the connection to be clean and tight, else a voltage drop will occur. The voltage drop fools the regulator into thinking the battery is charged, because the drop adds resistance to what the regulator sees. Because the effective resistance of the battery is very small, any added resistance makes the battery appear to the regulator to be charged. Anyway, I think the alternator is Ok.
You are wrong.  you should NEVER disconnect the battery when it is running...............and if the diodes are toast, it will still charge-----------then how do you know?


Posted By: ramblinfsj
Date Posted: Jan/06/2010 at 12:48pm
Originally posted by billd billd wrote:

And do NOT worry if it's under 14v. Specs for different batteries and different temps and charge states will vary. 13.5 is still just fine and in specs for most batteries. So if it's UNDER 14 or runs in the mid-13s you don't necessarily have anything at all wrong.
 
Yeah I shouldn't have said 14v period but around 14v.


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1982 Jeep J-20
1965 Rambler American 220
1978 Jeep Cherokee w/401
1983 Jeep J-10
1979 Concord DL 2dr


Posted By: billd
Date Posted: Jan/06/2010 at 12:50pm
Sometimes "close enough" counts, eh? LOL

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Posted By: kensamc
Date Posted: Jan/06/2010 at 1:02pm
Amby wagon with a 343 ..... that's on my "someday" list........

For now, happy with my preChrysler Jeep, my Eagles and my first big project, the 58 Cross Country.

Every confidence in AMC and that all these cars will be the only one of their kind
in my neighborhood or local cruise.....




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1986 Jeep Corp Grand Wagoneer



Posted By: billd
Date Posted: Jan/06/2010 at 1:05pm
You have a pretty nice collection listed in your sig area - nothing at all to be ashamed of, and I'd be happy to have a couple of 'em myself!

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Posted By: gwryder
Date Posted: Jan/06/2010 at 1:18pm
Billd,
True, a voltage regulator only senses voltage, but voltage is a function of Ohms law. The real brains in the system is the battery. The regulator only responds to voltage, while the alternator is a current device. All the resistances in the charging system will affect battery charging and voltage, that's why having all connections clean is important. Also, the engine should run ~ 2000 rpm for the alternator to put out enough current. Lower speeds will affect output. It's very likely that idling with accessories on will drain the battery.
To do this correctly, the specific gravity of the battery electrolite must be know. That's the only way one can tell the state of charge of the battery. If a battery is sulfated, the effective resistance is high, but the specific gravity is low, so the state of charge of the battery is low, even though the battery could  read ~14 volts, indicating a charged battery. With the battery voltage high, the regulator thinks the battery is charged, but the specific gravity will say it's not. I'm sure you've seen this in your days.
 
gwryder


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John
70 AMX





Posted By: ramblinfsj
Date Posted: Jan/06/2010 at 1:28pm
Originally posted by billd billd wrote:

You have a pretty nice collection listed in your sig area - nothing at all to be ashamed of, and I'd be happy to have a couple of 'em myself!
 
I totally agree. I have a hand full of AMC's myself and the one I will always have in my driveway is a Grand Wagoneer. They are the best in any situation............... except for fuel milage.


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1982 Jeep J-20
1965 Rambler American 220
1978 Jeep Cherokee w/401
1983 Jeep J-10
1979 Concord DL 2dr


Posted By: kensamc
Date Posted: Jan/06/2010 at 3:00pm
Bill

BTW, I need to update my signature .... succumbed to the economy and sold the Ambassador to Forest.
Also looking to sell one of the Eagles, but I'm guessing you like 'em a bit older .....


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1986 Jeep Corp Grand Wagoneer



Posted By: poormansMACHINE
Date Posted: Jan/06/2010 at 4:45pm
Originally posted by billd billd wrote:

Sometimes "close enough" counts, eh? LOL

In horse shoes and molotov coctails.



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