Battery light comes on
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Posting Guru
Joined: Jan 2000
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From: colbert washington
Battery light comes on
I put a new serpantine belt on my 98 F150 4.6 ltr. I did this because the battery light was comming on under load. The ammeter gage however did not fluctuate at all. I figured the belt was worn out and slipping under load. It is still lighting momentarly under load. Bad alternator I wonder the ammeter never shows drain. Anybody ever have this problem? Im hesitant to just replace the alt as this is the big alt for trailer package probably lots of $$$$.
Lead Driver
Joined: Sep 2006
Posts: 7,907
Likes: 143
You can have the unit tested for performance but still need to either service it or replace it.
Here is how the lamp works.
It has battery applied through the ignition switch.
The other side goes to the regulator mounted on the alternator.
When there is no charge the regulator provides a ground to light the lamp to tell you this fact.
Once the alternator rpm comes up to provide output, the regulator removes ground from the lamp so it goes out.
This tells you the alternator is outputting.
If it is intermittant, the alternator is faulty.
Likely brushes are worn and/or the commutator might be rough so the brushes can't keep solid contact at higher rpm.
Good luck.
Here is how the lamp works.
It has battery applied through the ignition switch.
The other side goes to the regulator mounted on the alternator.
When there is no charge the regulator provides a ground to light the lamp to tell you this fact.
Once the alternator rpm comes up to provide output, the regulator removes ground from the lamp so it goes out.
This tells you the alternator is outputting.
If it is intermittant, the alternator is faulty.
Likely brushes are worn and/or the commutator might be rough so the brushes can't keep solid contact at higher rpm.
Good luck.
Thread Starter
|
Posting Guru
Joined: Jan 2000
Posts: 2,281
Likes: 4
From: colbert washington
You can have the unit tested for performance but still need to either service it or replace it.
Here is how the lamp works.
It has battery applied through the ignition switch.
The other side goes to the regulator mounted on the alternator.
When there is no charge the regulator provides a ground to light the lamp to tell you this fact.
Once the alternator rpm comes up to provide output, the regulator removes ground from the lamp so it goes out.
This tells you the alternator is outputting.
If it is intermittant, the alternator is faulty.
Likely brushes are worn and/or the commutator might be rough so the brushes can't keep solid contact at higher rpm.
Good luck.
Here is how the lamp works.
It has battery applied through the ignition switch.
The other side goes to the regulator mounted on the alternator.
When there is no charge the regulator provides a ground to light the lamp to tell you this fact.
Once the alternator rpm comes up to provide output, the regulator removes ground from the lamp so it goes out.
This tells you the alternator is outputting.
If it is intermittant, the alternator is faulty.
Likely brushes are worn and/or the commutator might be rough so the brushes can't keep solid contact at higher rpm.
Good luck.
New User
Joined: Sep 2011
Posts: 15
Likes: 0
From: Normally, Nashville
Just recently I was having the same issue with my vehicle. I pulled my alt and had it tested. They handed back to me and told me it was working great... Still, my battery light was on, my head lights didnt seem normal, nothing seemed up to par. So, I did a little research and found out that when your alt is going bad it messes with your battery (but we all already knew that), but that being said my alt read high on my gauge when under load trying to charge the batter, but normal when at idle. Turns out it was over working trying to output the amps the car needed while still reading fairly normal volts. I replaced the alt and it made a world of difference.
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