2000 GT- Alternator not charging

[grugug]

Hey Everyone,
I recently purchased a 2000 Mustang GT. On the drive home, about an hour in, I noticed the odometer turned off, lights started flickering and eventually the car died. After getting it home, I ran a few tests and it appeared that the alternator wasn’t charging. When measuring using the alternator casing as the ground, the multi meter read the same voltage as the battery. I removed the alternator and got it bench tested at autozone and it output 14.8 volts. I also checked the small clip connector with the 2 wires, and they both had voltage coming through. The yellow was reading the same as the battery, however the green/red one was reading significantly lower.

One note is that when the car died, i don’t remember seeing the “low battery” dash light come on. When i put the ignition to on, the battery light also does not come on.

Any ideas? I’ve read that if the battery dash light burns out, that will cause problems in ur charging system. Any way to verify that?

Thanks!

 

[squeak93]

For the battery light you'll need to pull the cluster and check/replace. That is fairly simple in itself. I'm not sure I've seen the light out will cause issues but its a simple check and worth running.

Another question - Are you getting fuel?

 

[grugug]

For the battery light you'll need to pull the cluster and check/replace. That is fairly simple in itself. I'm not sure I've seen the light out will cause issues but its a simple check and worth running.

Another question - Are you getting fuel?

Yep fuel is all good. it runs great until the battery dies from not being charged by the alternator.

 

[nickyb]

Mega fuse???????
Ask me how I know.

 

[grugug]

Mega fuse???????
Ask me how I know.

From what i understand this year doesn’t have mega fuses and instead uses fusible links. If one of those were blown wouldn’t I not have connectivity between the battery and alternator? Thanks!

 

[nickyb]

They DO have a fuse, its in the under hood fuse panel.

 

[grugug]

They DO have a fuse, its in the under hood fuse panel.

They DO have a fuse, its in the under hood fuse panel.

Is it a MEGA fuse or a normal one? I checked all of the normal fuses in the under hood box and none of them were blown

 

[nickyb]

Its not a mega fuse, but its location is under hood fuse box, so if you tested all of them with a multimeter then it ain't that.

 

[squeak93]

The wire between alt and post should have a fuseable link. If its blown you are correct, no connect. The battery to post is just a standard battery cable. YOu can always put a temp cable from alt post to dist box post to see if that charges then.

Remember while testing this that the alt will not charge a dead battery up but to your point, you should be able to disconnect the batt while the car is running and it run off the alt just fine.

 

[grugug]

The wire between alt and post should have a fuseable link. If its blown you are correct, no connect. The battery to post is just a standard battery cable. YOu can always put a temp cable from alt post to dist box post to see if that charges then.

Remember while testing this that the alt will not charge a dead battery up but to your point, you should be able to disconnect the batt while the car is running and it run off the alt just fine.

Yeah I don’t think it’s one of those fusible links since i was able to verify that the alternator and the battery were connected. It seems more that the alternator is capable of charging, but for some reason the car isn’t telling it to charge.

 

[squeak93]

The alts are internally regulated if I remember correctly.

Self-Sensing Voltage Control. The internal regulator uses a dedicated "sense" wire (Pin B on the 3-wire plug) connected to constant battery voltage. It automatically increases or decreases field current to hold system voltage steady around 13.8V to 14.5V regardless of engine RPM.