Bad Alt. Or what?

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tjh566

New Member

May 22, 2004

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Northern Va

Jul 7, 2007

#1

• Jul 7, 2007

• #1

Ok so heres the deal, When I first fire up the car and start to cruise the voltage is like 13.5-13.7, after awhile of driving, the voltage slowly decreases down to like 12.3-12.5, then stays there the rest of the time, I think it has something to do with heat but idk. whatca guys think?

 

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cbarr300

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Jun 6, 2006

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goose creek, SC

Jul 7, 2007

#2

• Jul 7, 2007

• #2

attach a ground from your battery to your alternator casing and see what that does for you.

 

HISSIN50

"How long does it take to get help in here?

15 Year Member

Nov 29, 1999

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Jul 8, 2007

#3

• Jul 8, 2007

• #3

I'd agree about the heat. Doing as Clay outlined is useful. You can also check the regulator wiring to see if it's all vulcanized. When it's at 12.5 volts, you are discharging the system.

And since it acts up when hot, you could drive to the parts store and let them do a dynamic test on the system.

Good luck.

 

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bmac50

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Oct 18, 2006

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Florida

Jul 8, 2007

#4

• Jul 8, 2007

• #4

tjh566 said:

Ok so heres the deal, When I first fire up the car and start to cruise the voltage is like 13.5-13.7, after awhile of driving, the voltage slowly decreases down to like 12.3-12.5, then stays there the rest of the time, I think it has something to do with heat but idk. whatca guys think?

Click to expand...

You say, "the voltage slowly decreases down to like 12.3-12.5", measured with what? If it's a Ford gauge that would be about and that's what mine showed with a brand new alternator. Stock alternator puts out 130 amps when as less juice is needed it goes back to roughly 87 amps, in underpulleys probably a bit less. I used a ten foot pair of leads I borrowed so I could drive and see what was going on. My guage was lower than I thought it should be but the meter never went below 12.8.

 

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tjh566

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May 22, 2004

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Northern Va

Jul 8, 2007

#5

• Jul 8, 2007

• #5

cbarr300 said:

attach a ground from your battery to your alternator casing and see what that does for you.

Click to expand...

I attached a ground from the alt to the body not too long ago, it got me higher voltages when starting out but then as I drove around for awhile It did the same. Attaching one to the battery isnt really an option since Ive relocated my batt to my trunk for the meth injection system.


I took the alt off a few weeks ago and had it tested it tessted as all good, but to me 12.3-12.5 volts isnt enough... or is it?

edit: I have stock pulleys, No underdrives.

 

HISSIN50

"How long does it take to get help in here?

15 Year Member

Nov 29, 1999

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Jul 8, 2007

#6

• Jul 8, 2007

• #6

Again, 12.3-12.5 volts is discharging.
Is it possible you're seeing a huge voltage drop in the system? How does voltage at the alternator's charge stud compare to that at the battery itself? If it's more than a couple hundred mV, that's unacceptable to me.

Is your sense wiring still the way it was from the factory? The point of that circuit is to monitor alternator output vs what the regulator remotely senses near the battery. Now that your battery is not near the sense receptor, the alt might not know you're dropping so much current to the battery. Otherwise, it would be kicking alt output up.

Good luck.

 

blksn955.o

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Mar 15, 2002

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st.louis mo 314

Jul 8, 2007

#7

• Jul 8, 2007

• #7

Just asking...

Is either the alt. or brackets painted or powdercoted? The alt. grounds threw the brackets and if there is not a good contact at the alt. or bracket then it could also seem weak.

I found out the hard way when I had my alt. case and brackets powdercoated. They would not allow a good ground. I had to sand down the area of contact to get a good ground. I tested this by running a 8ga wire from one of the alt. case bolts (there are 3 of them) to the strut tower bolt on the pass. side. Started charging correctly instantly and then took off the alt. and sanded the areas of contact.

 

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cbarr300

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Jun 6, 2006

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goose creek, SC

Jul 8, 2007

#8

• Jul 8, 2007

• #8

do you have any problem with the car cranking slower after you run the car for a while?

 

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tjh566

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May 22, 2004

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Northern Va

Jul 9, 2007

#9

• Jul 9, 2007

• #9

Yes I do actually.

All the wiring is the same, I just took the positive battery cable and put it on the distribution box and the negavtive battery cable to the inner fender of the car.

All connections are clean and free of paint.

And Ill test the voltage difference at the battery and alt probly this weekend.

 

blksn955.o

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Mar 15, 2002

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st.louis mo 314

Jul 9, 2007

#10

• Jul 9, 2007

• #10

might be worth checking your major grounds like block to chassis, batt. to block, and batt. to chassis.

its fast to check and easy to fix.

 

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cbarr300

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Jun 6, 2006

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goose creek, SC

Jul 9, 2007

#11

• Jul 9, 2007

• #11

that definitely sounds like a ground problem with me. It is exactly like mine. If you haven't already, attach a wire from the negative (or chassis if you have your battery in the trunk) to the alternator casing....then see if it's putting out a better charge when you attach it.

 

rude_life

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Mar 30, 2005

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Jul 27, 2007

#12

• Jul 27, 2007

• #12

How's everyone doing..I have the SAME symptoms with mine and..This might sound bad but..How do you attach a ground from your alternator to your battery and what does that do for the voltage?