02 ex alternator not charging

1badpsd

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My mother has an 02 excursion. And the alternator isn't charging, was working fine she parked got home and parked it at 4:45 and by 6 the battery's were completely drained. I went and swapped alternators thinking simple with another new alternator and no change, not charging at all. I had to leave but does anyone have any insight of best place to start when I get back to it?
 

lincolnlocker

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My mother has an 02 excursion. And the alternator isn't charging, was working fine she parked got home and parked it at 4:45 and by 6 the battery's were completely drained. I went and swapped alternators thinking simple with another new alternator and no change, not charging at all. I had to leave but does anyone have any insight of best place to start when I get back to it?
check signal voltage at the 2 post plug with key on.

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psduser1

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If it drained the batteries after she parked it-not running-you may have a parasitic drain, and the alternator just can't keep up when it's running.
Just how I read the op.:shrug:
 

sootie

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or there is a short in one/both batteries which creates a power sink. try isolating them one at a time and see if anything changes. You could also do a test with a multi meter. take the terminals off the battery. Set the multimeter on VDC. Pop the caps off the top so you can see the acid. Put the red lead on the positive post and dip the black lead in the acid in the first cell. Write the number down. Move the black lead to the next cell. they should all increase by 1.5 volts. If there is one that reads zero or is a much higher number, you have a bad cell or a short.
 

lincolnlocker

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or there is a short in one/both batteries which creates a power sink. try isolating them one at a time and see if anything changes. You could also do a test with a multi meter. take the terminals off the battery. Set the multimeter on VDC. Pop the caps off the top so you can see the acid. Put the red lead on the positive post and dip the black lead in the acid in the first cell. Write the number down. Move the black lead to the next cell. they should all increase by 1.5 volts. If there is one that reads zero or is a much higher number, you have a bad cell or a short.
that is a very useful tid bit about testing a battery. good to know..

would a simple load test tell that also?

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sootie

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that is a very useful tid bit about testing a battery. good to know..

would a simple load test tell that also?

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it would but can be deceiving if the battery has been run down, or just came off a charge. We learned that trick working on big equipment batteries that have replaceable cells.
 

1badpsd

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Finally had a few minutes to get over and look at it. It is in fact not putting a drain on the batteries, I guess when thos started they were just that drained. I didn't have a multi meter with me, but I checked the passenger battery ground, replaced the entire positive cable(its needed replacing), the plug on the alternator and the terminal end on the hot wire and still no change. I did put the old (brand new) alternator back on and the battery light went away but still won't charge.
 

lincolnlocker

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Finally had a few minutes to get over and look at it. It is in fact not putting a drain on the batteries, I guess when thos started they were just that drained. I didn't have a multi meter with me, but I checked the passenger battery ground, replaced the entire positive cable(its needed replacing), the plug on the alternator and the terminal end on the hot wire and still no change. I did put the old (brand new) alternator back on and the battery light went away but still won't charge.

if you didn't have a multi meter, how do you know it wasnt charging?

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psduser1

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So did you fully charge the batteries before testing?
Depending how long it's been like this, you may need new batteries as well as a new alternator.
Might try sooties suggestion for the battery side. Worn out batteries will kill an alternator!
 

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