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post #11 of (permalink) Old 02-25-2005, 07:43 AM
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Re: Overcharging Alternator (Delco 3 wire hook up)

13.5-14 volts
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post #12 of (permalink) Old 02-25-2005, 08:06 AM
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Re: Overcharging Alternator (Delco 3 wire hook up)

[ QUOTE ]
What should a stock alt put out at idle any way?

[/ QUOTE ]

No more than about 14.8 volts under any circumstances.

Depending on the idle speed, pulley ratio and alternator size, the current output might be from just a few amps to twenty or more. But if the battery is fully charged the alternator will only put out what is actually being used by the ignition system and accessories.
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post #13 of (permalink) Old 02-25-2005, 10:46 AM
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Re: Overcharging Alternator (Delco 3 wire hook up)

I've had this problem due to corroded connections. Just as describe above, the sense wire. Also wondering how you are measuring the voltage. The stock guage on mine, exaggerates deviations from normal. IE, anything above or below around 14 volts looks way further off than it actually is. A digital multimeter would be better for testing purposes.
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post #14 of (permalink) Old 02-25-2005, 11:16 AM Thread Starter
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Re: Overcharging Alternator (Delco 3 wire hook up)

Still haven't had to time check it out because my Jeep garage is at different location than my house. FYI though - I am using a digital multimeter for the readings. My stock volt gauge is actually reading low at about 12 volts but it may be fried now after driving the Jeep at 17.5 volts.
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post #15 of (permalink) Old 02-25-2005, 02:18 PM
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Re: Overcharging Alternator (Delco 3 wire hook up)

Off the top, it sounds like the regulator took a dump

First, make sure all of your electrical connections are good ... tight, no corrosion, etc.

Measure the float voltage at the point where the big fat wire from the alternator connects into the rest of the electrical circuit with the engine running and all electrics OFF. The voltage should be 14.7 volts a little bit. Anything greater than 15 volts probably means the alternator and/or regulator committed suicide.

Once you get the charging problem worked out, do yourself a favod and measure the voltage drop across the big wire that connects to the alternator output. If you measure more than 0.1 volt, replace it with a direct connection to the positive side of the battery.
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post #16 of (permalink) Old 02-25-2005, 08:22 PM Thread Starter
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Re: Overcharging Alternator (Delco 3 wire hook up)

OK - I looked at the Jeep for 15 minutes tonight and now I have some more questions. I have been reading this OLD POST that contains some info from RRich on what the 3 terminals do on the Delco style alternator. My question involves the terminals labeled #1 and #2 on the side.

Is this correct:

#1 - feeds the alternator idiot light to indicate if the alternator is charging

#2 - the "sense" wire that tells the alternator if it is putting out the proper voltage. This wire is spliced into the main output wire off the terminal on the back of the alternator

If so then the PO switched the wires on the plug that fits into the alternator( plug is spliced on). The weird thing is that this is how it has always been because the plug only goes on one way. Also, the alternator that I took off looks identical to the one from the Waggy (and the one on my scrambler) but the side terminals are NOT labeled - there is no #1/#2 embossed on the back of the alternator.

Last question: I don't have an alternator indicator lamp on my dash so do I need the wire from terminal #1? It's freezing here and I just put my harness back together [img]images/graemlins/cussing.gif[/img] so I'm not too excited about tearing it apart to chase this wire!

Thanks!
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post #17 of (permalink) Old 02-26-2005, 12:02 AM
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Re: Overcharging Alternator (Delco 3 wire hook up)

If those 2 small wires are reversed it could very well be the reason it's overcharging.

Make it easy on yourself - don't trust the PO, his wiring, or his wire colors.
Get a new connector from the parts house - with short wires already attached - about $4?

On that connector you'll find a red wire and either a white or brown wire.

The red wire is the sense line. I honestly don't remember if it's #1 or #2 or A or B.
Run the red wire direct to the battery, not to the output of the alternator, and not spliced into the output wire. Make a new separate wire directly to the battery (+) terminal. That's very important if you want it to charge properly.
That's the "sense" line that determines if, and how much the battery needs to be charged. Running it anywhere else is just fooling - lying - to the regulator.

The other wire, usually white, but sometimes brown, goes to the idiot light. If you don't have a light, you need to go to a Radio Shack, get a 10 or 15 Ohm, 1 Watt resistor and a 10 amp Diode.
Wire it from that white (or brown) wire on the new connector to the diode - put that wire on the "cathode" or stripe end.
Put the other end of the diode to the resistor.
Put the other end of the resistor to IGN (+).

That wire energizes the field in the alternator. Without it the alternator has trouble getting started charging. The diode prevents it from backfeeding the ignition - making it impossible to shut the engine off.


Sounds like you have those two wires reversed right now - the "sense" line isn't "seeing" enough voltage, causing the regulator to "think" the battery is undercharged. It "tells" the alternator to go "full blast."

The battery won't last long being overcharged.

I really doubt you've damaged anything -- yet.

Shouldn't be a major task - even in the cold.

Let us know how it turns out.
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post #18 of (permalink) Old 02-27-2005, 07:47 PM Thread Starter
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Re: Overcharging Alternator (Delco 3 wire hook up)

Well . . . do want the good news or the bad news?

Personally, I like to start with the bad and end with the good.

Bad news - I have have wasted everyone's time who posted in this thread. Turns out that my multimeter had a low battery and that's what caused the improper reading. Something just didn't seem right so I check 2 other vehicles at my garage and all of them read 17+ volts at the battery! [img]images/graemlins/wall.gif[/img]

I changed the battery and voila my overcharging alternator problem magically went away!

However, the good news (for me anyway) is that I learned a little more about the Jeep in the process and may have found the source of the constant battery drain. The wires on the alternator (terminal #1 and #2) were switched because the PO wired the plug wrong. I wired them up as RRich suggested so we'll see if she starts next time I make it to the garage. FYI - the #1 terminal is the excitor wire and the #2 terminal is the sense wire.

Sorry - and I humbly accept your [img]images/graemlins/chair.gif[/img]!
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post #19 of (permalink) Old 02-27-2005, 09:09 PM
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Re: Overcharging Alternator (Delco 3 wire hook up)

I hate when that Happens!! least you figured it out before a 100.00 parts store run!!
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post #20 of (permalink) Old 02-27-2005, 09:12 PM
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Re: Overcharging Alternator (Delco 3 wire hook up)

[ QUOTE ]
I hate when that Happens!! least you figured it out before a 100.00 parts store run!!

[/ QUOTE ]

Not only that he had what it takes to come back and tell us about it. [img]images/graemlins/thumbsup.gif[/img]

[img]images/graemlins/applause.gif[/img] For the follow up.

[img]images/graemlins/40BEER.gif[/img]
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