alternator help!!!!

[DARKTSI]

ok so i just finished my swap its a 95 talon tsi awd...started driving my car and it drove fine all day but then at night i drove it for a little bit like 4 miles then out of no where it started stumbling and my headlights started to get dimmer and dimmer also all the lights on my dash turned on......i think it whent into limp home mode because it wouldnt go over certain rpm....but hen i put it in lower gear since its auto it reved higher......but yea my question is ...my battery is new so


is it my alternator?
a fuse or wat?

should i adjust it?
or replace it?


i tested it i got car off battery voltage is 11 when it used to be 12 sumthing
car on battery voltage is the same but slowly starts dropping after a while
ad alternator voltage is the same as the battery and then starts dropping with it

 

[Jetrosr]

Sounds alot like a bad alternator. You sould see at least 13.5 at the battery with the engine running, at least 12.6 with the engine off and battery charged up.

 

[GRAVEDIGGER]

You need to replace your alternator. With the car running you should have somewhere between 12.8 and 14.2 volts. If you don't then you need to replace your alternator.

 

[Dave532]

I understand you just did a motor swap? I would suggest making sure ALL your grounds are attached.

Assuming you have no physical alternator belt issues...

The electrical system should be something like this:

Engine running, battery needs a charge: around 14.8 v
If less, battery may be fully charged. If battery is not full charged, alternator is suspect.

Engine running, battery fully charged: around 13.8 v
If less, then the alternator or cables, ground straps are suspect.

Engine not running, battery charged: around 12.6 v
If less, then battery is not fully charged or suspect

Numerous auto shops will also test your alternator\battery for free.