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Confirm an alternator conclusion?

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kensamc View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote kensamc Quote  Post ReplyReply Direct Link To This Post Posted: Jan/06/2010 at 10:58am

  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.
1986 Jeep Corp Grand Wagoneer

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billd View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote billd Quote  Post ReplyReply Direct Link To This Post Posted: Jan/06/2010 at 12:05pm
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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Post Options Post Options   Thanks (0) Thanks(0)   Quote ramblinfsj Quote  Post ReplyReply Direct Link To This Post Posted: Jan/06/2010 at 12:25pm
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.
1982 Jeep J-20
1965 Rambler American 220
1978 Jeep Cherokee w/401
1962 Rambler Classic 400
1973 DJ-5 Postal Jeep
1979 Concord DL 2dr
1975 Matador Wagon
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Post Options Post Options   Thanks (0) Thanks(0)   Quote billd Quote  Post ReplyReply Direct Link To This Post Posted: Jan/06/2010 at 12:32pm
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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Post Options Post Options   Thanks (0) Thanks(0)   Quote gwryder Quote  Post ReplyReply Direct Link To This Post Posted: Jan/06/2010 at 12:33pm

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.
John
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Post Options Post Options   Thanks (0) Thanks(0)   Quote billd Quote  Post ReplyReply Direct Link To This Post Posted: Jan/06/2010 at 12:54pm
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.



Edited by billd - Jan/06/2010 at 1:06pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote kensamc Quote  Post ReplyReply Direct Link To This Post Posted: Jan/06/2010 at 1:01pm

 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 .....




1986 Jeep Corp Grand Wagoneer

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Post Options Post Options   Thanks (0) Thanks(0)   Quote billd Quote  Post ReplyReply Direct Link To This Post Posted: Jan/06/2010 at 1:17pm
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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Post Options Post Options   Thanks (0) Thanks(0)   Quote purple72Gremlin Quote  Post ReplyReply Direct Link To This Post Posted: Jan/06/2010 at 1:23pm
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?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote ramblinfsj Quote  Post ReplyReply Direct Link To This Post Posted: Jan/06/2010 at 1:48pm
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.
1982 Jeep J-20
1965 Rambler American 220
1978 Jeep Cherokee w/401
1962 Rambler Classic 400
1973 DJ-5 Postal Jeep
1979 Concord DL 2dr
1975 Matador Wagon
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