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Confirm an alternator conclusion?

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poormansMACHINE View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote poormansMACHINE Quote  Post ReplyReply Direct Link To This Post Topic: Confirm an alternator conclusion?
    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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Post Options Post Options   Thanks (0) Thanks(0)   Quote kensamc Quote  Post ReplyReply Direct Link To This Post 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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Post Options Post Options   Thanks (0) Thanks(0)   Quote ramblinfsj Quote  Post ReplyReply Direct Link To This Post 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.
1982 Jeep J-20
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1978 Jeep Cherokee w/401
1983 Jeep J-10
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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 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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Post Options Post Options   Thanks (0) Thanks(0)   Quote billd Quote  Post ReplyReply Direct Link To This Post 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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Post Options Post Options   Thanks (0) Thanks(0)   Quote kensamc Quote  Post ReplyReply Direct Link To This Post 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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Post Options Post Options   Thanks (0) Thanks(0)   Quote billd Quote  Post ReplyReply Direct Link To This Post Posted: Jan/06/2010 at 12:50pm
Sometimes "close enough" counts, eh? LOL
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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 12:48pm
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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1978 Jeep Cherokee w/401
1983 Jeep J-10
1979 Concord DL 2dr
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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 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?
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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 12:17pm
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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