Alternator not charging?

Tiny
SUMMERWIND
  • MEMBER
  • 1993 FORD RANGER
I Replaced my alternator after the bearing went out. The unit was still charging but making a lot of noise. The new alternator(not rebuilt) was installed but would not put out more than 11 - 12 volts. I took it to the auto parts store I purchased it from they used a portable tester to confirm not charging. The battery is good, so I removed the catenator and took it back and they tested it on the bench 3 times and it passed every time. So I reinstalled it checked for good connections on the wiring, cleaned the battery posts, and still would not charge. My question is what now, how do I check the wiring to see if any of it is bad?
Monday, December 15th, 2008 AT 10:50 PM

18 Replies

Tiny
BLUELIGHTNIN6
  • MECHANIC
  • 16,542 POSTS
The wire from the alternator to the positive terminal (which runs the actual charge to your battery positive terminal) can sometimes go bad. You can bypass it by adding a wire at the small post, near the back of the alternator, then run it to the positive battery cable. The original wire is the small one which runs, attached, alongside the battery cable. Bypassing it will let you see if it is bad or not.

Hope this helps.
Thanks for using 2carpros. Com!
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Tuesday, December 16th, 2008 AT 1:27 AM
Tiny
JOE1953
  • MEMBER
  • 793 POSTS
  • 1993 FORD RANGER
  • 2.3L
  • 4 CYL
  • 2WD
  • MANUAL
  • 189,000 MILES
When the engine is idling the Alternator Charge about 13.7 Volts when turn head lights on it drop to 11.2 Volts and the Battry Show Low Charge is the Alternator going bad?
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Thursday, December 10th, 2020 AT 8:42 AM (Merged)
Tiny
WRENCHTECH
  • MECHANIC
  • 20,761 POSTS
The alternator could be bad. It's normal for it too drop somewhat at idle when accessories are turned on because it's just not spinning fast enough to keep up with the consumption but it shouldn't be dropping that much.
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Thursday, December 10th, 2020 AT 8:42 AM (Merged)
Tiny
JOE1953
  • MEMBER
  • 793 POSTS
Which is the best way to check the Alternator out to see is it bad what could be wrong with it, can it be repair?
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Thursday, December 10th, 2020 AT 8:42 AM (Merged)
Tiny
WRENCHTECH
  • MECHANIC
  • 20,761 POSTS
No, you don't repair alternators. You replace them. This one may have an external regulator too.
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Thursday, December 10th, 2020 AT 8:42 AM (Merged)
Tiny
P-COLAVETTE
  • MEMBER
  • 4 POSTS
  • 1992 FORD RANGER
Electrical problem
1992 Ford Ranger 4 cyl Two Wheel Drive 93,000 miles

I Have replaced: Battery, Altenator, Alt. Field 15 amp fuse(Underhood fuse box) 30 amp fuse in pass. Comp, cleaned Batt. Cables & Batt. Post, all cables connecting to starter solenoid on fenderwell underhood, and it STILL isn't charging while engine is running. Can anybody help?
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Thursday, December 10th, 2020 AT 8:42 AM (Merged)
Tiny
DAVE H
  • MECHANIC
  • 13,384 POSTS
Use a voltmeter red probe to alternator B+ connector and black probe to a ground .. you should be getting 13 + volts with engine running @ idle if oyur not alternator is bad still ... have you checked the fusible link in cable from alternator to battery !


https://www.2carpros.com/forum/automotive_pictures/266999_f150_3.jpg

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Thursday, December 10th, 2020 AT 8:42 AM (Merged)
Tiny
P-COLAVETTE
  • MEMBER
  • 4 POSTS
Yes, I have checked fusible link, it's good. I am beginning to think that the "Exciter" wire which supplies 12v to the alt. Is not doing it's job. If you can help me fix this problem, I will make a donation to the board, however, I believe in payment after service has been successfully rendered ! Thank's, Steve.
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Thursday, December 10th, 2020 AT 8:42 AM (Merged)
Tiny
DAVE H
  • MECHANIC
  • 13,384 POSTS
What is the actual engine size of the vehicle? 2.9L/3.0L?
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Thursday, December 10th, 2020 AT 8:42 AM (Merged)
Tiny
P-COLAVETTE
  • MEMBER
  • 4 POSTS
The vehicle is equipped with the 2.3L 4 cyl.
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Thursday, December 10th, 2020 AT 8:42 AM (Merged)
Tiny
DAVE H
  • MECHANIC
  • 13,384 POSTS
Check fuse #4 in underhood fuse box ..


https://www.2carpros.com/forum/automotive_pictures/266999_fuse_19.jpg



https://www.2carpros.com/forum/automotive_pictures/266999_fuse2_6.jpg



Also do you have a voltmeter ?
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Thursday, December 10th, 2020 AT 8:42 AM (Merged)
Tiny
P-COLAVETTE
  • MEMBER
  • 4 POSTS
Thank's All for the feedback ! I took the truck to a local shop yesterday, and after much Head Scratching & Foot Shuffling, it was determined that the underhood fuse block was incorrectly labeled ! The slot that was labeled as being the 15 amp ALT. Field slot, was not. The slot directly across from it turned out to be where the 15 amp fuse needed to be installed to energize the ALT. FLD with the voltage needed to cause the altenator to charge ! She's charging like a champ now ! Once Again, Many Thank's, Steve.
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Thursday, December 10th, 2020 AT 8:42 AM (Merged)
Tiny
DAVE H
  • MECHANIC
  • 13,384 POSTS
Could you explain which fuse is wrong for future aid to other people? Is my diagram of the fuse box wrong?
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Thursday, December 10th, 2020 AT 8:42 AM (Merged)
Tiny
TYLER PHILLIPS
  • MEMBER
  • 1 POST
  • 1992 FORD RANGER
  • 4.0L
  • V6
  • 4WD
  • AUTOMATIC
  • 195,000 MILES
Had alternator checked at Autozone. Passed test. I have replaced battery three times now and each drags down. Will start about eight times but after that will not crank. But if it is running will stay running. Could alternator be putting out just enough volts to keep it running?
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Thursday, December 10th, 2020 AT 8:42 AM (Merged)
Tiny
STEVE W.
  • MECHANIC
  • 15,233 POSTS
Charge the battery. Measure the voltage at the terminals you want to see 12.4-12.6 volts depending on how well it charged. Start the engine. Measure the voltage again. You should see between 13.4-14 volts depending on what the regulator is doing.
If you do the alternator is working. Then take it to a shop and have them actually test the current draw of the starter itself.

The next step would be to look for a parasitic draw. For this you need a couple items. A voltmeter that reads millivolts and a couple charts that you can download. Instead of me telling you how to do the test you can watch Charles. He also shows the link to the charts you need.
https://www.youtube.com/watch?v=lRcj1fQcWwU
Good luck.
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Thursday, December 10th, 2020 AT 8:42 AM (Merged)
Tiny
RENEE L
  • ADMIN
  • 1,260 POSTS
Hello TYLER PHILLIPS,

In addition to the you tube video Steve W sent you here is a link to an article on this site with step by step instructors, pictures and a video for you to check for a parasitic draw. I hope this helps you.

https://www.2carpros.com/articles/car-battery-dead-overnight

Thank you for visiting 2CarPros and have a great rest of your day!

Kindest regards,

Renee
Admin
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Thursday, December 10th, 2020 AT 8:42 AM (Merged)
Tiny
DAVID CHESNEY
  • MEMBER
  • 1 POST
  • 1990 FORD RANGER
  • 4 CYL
  • 2WD
  • AUTOMATIC
  • 175,000 MILES
After replacing the alternator and the battery and serpintine belt vehicle still not charging and dash light for the battery is still on. And voltage meter only reading 10 volts
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Thursday, December 10th, 2020 AT 8:42 AM (Merged)
Tiny
RASMATAZ
  • MECHANIC
  • 75,992 POSTS
Double check all connection at battery and alternator if okay ground the F screw to full field the alternator if it increase doing this-replace the voltage regulator.


https://www.2carpros.com/forum/automotive_pictures/12900_ford_ranger_charge_system_1.jpg

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Thursday, December 10th, 2020 AT 8:42 AM (Merged)

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