Alternator not charging battery

Tiny
DSQUARE63
  • 1998 MERCURY SABLE
  • 6 CYL
  • FWD
  • AUTOMATIC
  • 110 MILES

We've replaced the alternator and ground wires - will not charge battery?

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Wednesday, December 29th, 2010 AT 6:57 PM

18 Replies

Tiny
KHLOW2008
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Did you test the replacement alternator?
There are no guarantee used or reman alternators wuld be good.

At the alternator main mast, test for battery voltage. If voltage is not present or much lower than battery voltage, the connection between battery and alternator is bad.

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Wednesday, December 29th, 2010 AT 7:38 PM
Tiny
DSQUARE63
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We have already checked the alternator - it is brand new. We have also checked the battery voltage connection.

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Wednesday, December 29th, 2010 AT 7:45 PM
Tiny
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Attached is a schematic of the charging system.

The followng must be hot at all times :

1. Yellow/White wire.
2. Orange/Light Blue wire. (Disconnect to test)

Is the charge indicator light showing when igniton switch is turned on?
Does charge indicator light turn off when engine is started?
What is the voltage at B+ (Yellow/White wire) when engine is not running?
What is the voltage at B+ (Yellow/White wire) when engine is running?
What is the voltage between battery terminals when engine is not running?
What is the voltage between battery terminals when engine is running?

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Thursday, December 30th, 2010 AT 1:13 PM
Tiny
DSQUARE63
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Yes the light is on with key and runnin. Both wires are hot. And the voltage on all those questions is not running it is about 12.4 when you start it drops to about 10.6 and as it runs it drops

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Saturday, January 1st, 2011 AT 9:26 PM
Tiny
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Check the crank pully harmonic damper. If you have abnormal belting noises and the pulley on which the alternator drive belt is seated on seems to be wavy, the damper could be bad resulting in the alternator running at a lowe r than required speed due to slipping.

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Sunday, January 2nd, 2011 AT 3:06 AM
Tiny
DSQUARE63
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That all looks good voltage doest go up either if you raise it up off of idle.I got it to charge 1 when I re did all the ground wire it jumped to 15.3 volts turned on headlights fine turned on rear defrost and it quit and I cant get it to do anything now

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Sunday, January 2nd, 2011 AT 3:17 AM
Tiny
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Have the battery recharged and retest.

When charging voltage drops, it could mean the alternator is not turning at the required speed or it is bad.

Check for blown fuses.

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Sunday, January 2nd, 2011 AT 4:55 AM
Tiny
DSQUARE63
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All fuses look goods I will charge battery and do load test it would be nice if it was that but if u run the car till it dies from low voltage if u let sit for as while battery will chagre it self back up

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Sunday, January 2nd, 2011 AT 5:11 PM
Tiny
KHLOW2008
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Yes, that indicates the charging system is at fault.

Have you confirmed the crankpully is good?

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Sunday, January 2nd, 2011 AT 5:20 PM
Tiny
DSQUARE63
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No I havent what just runn it and give it a visiual inspection spining

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Sunday, January 2nd, 2011 AT 6:34 PM
Tiny
DSQUARE63
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Pully looks good some body told me the positive starter wire could b the prob 2 but that doesnt sound right

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Sunday, January 2nd, 2011 AT 10:41 PM
Tiny
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Pully might look good but you need to confirm it is good. Looking does not confirm it is good as it can be deceptive.

Use marker to make a mark on outer ring of pulley an another near centeral ring and note if the outer ring moves away from the mark when engine is running.

" yes the light is on with key and runnin. Both wires are hot. And the voltage on all those questions is not running it is about 12.4 when you start it drops to about 10.6 and as it runs it drops"

One of your reply mentioned this. The drop to 10.6 vlots, whare was it measured, between battery post? Was the voltage between the alternator main post and ground tested?

Starter cable is not involved unless alternator main wire is joined from there.

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Monday, January 3rd, 2011 AT 1:51 PM
Tiny
DSQUARE63
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It is the same at battery and on back of alternator

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Monday, January 3rd, 2011 AT 7:57 PM
Tiny
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Either the alternator or pulley is bad.

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Monday, January 3rd, 2011 AT 8:44 PM
Tiny
DSQUARE63
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Put marks all over pully they all stayed lined up I pulled the tree prong plug on back of alternator voltage stayed same at battery and touched the prongs in alternator with test light nothing then the plug the orange with a blue stripe barley light test light the other two nothing I did all that with car running on all my test the voltage at battery and at alternator have been the same

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Monday, January 3rd, 2011 AT 11:39 PM
Tiny
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The Orange/Light Blue wire should have battery voltage. With engine off, unplug the alternator and test the Orange/Light Blue wire. If voltage is not avaliable or not battery voltage, check the voltage at alternator fuse # 26 in engine compartment fuse and relay box.

If battery voltage is available, check for poor continuity between fuse and alternator.

Try applying battery voltage to Orange/Light Blue wire and test if charging is as desired.

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Tuesday, January 4th, 2011 AT 2:21 PM
Tiny
94_DEVILLE
  • MEMBER

My battery and alternator were tested. Its a rebuild though. I have also replaced the pulleys and belt. Everything is all on correctly. Something is just causing my car to die. It runs fine for a day or two after the repair but if I let the car sit then it dies.

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Wednesday, March 22nd, 2017 AT 6:34 AM
Tiny
CARADIODOC
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You need to start a new question. We don't know your brand, model, year, engine size, mileage, or transmission type. You aren't clear as to what "dying" means. Do you mean electrical system or engine? This was a six-year-old conversation between two people. It is already listed as having received a reply, so none of the other experts are going to see your addition or have a chance to reply to it. That isn't going to help you.

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Wednesday, March 22nd, 2017 AT 6:17 PM

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