My 2002 Maxima, 3.5L alternator is not properly charging and I can not figure out why.

Driving home the other day, the car died. I assumed it was the alternator going bad. So i replaced the alternator with another alternator I had. I brought the alternator to Autozone before installing and tested it. Passed all tests and showed an output voltage of 14.5V. Also the alternator I used was fully working a week ago on another car.

I charged the battery and started the car. Checked the voltage across the battery and it only read 12.5V. I checked the ALT 10A fuse under the hood and it was fine. Next I removed the two 10mm bolts holding the fusible link between the battery and alternator (on the positive wire of battery) and replaced the 120A Fuse. I cleaned the contacts and tightened the two 10mm bolts down tight. Turned the car on and tested the voltage between the alternator power wire and the positive terminal on the battery. No difference. Moved the probe to measure the voltage potential between the alternator and the negative of the battery and it was only 12.3V.

Probably should have started with this, but next turned the key into the ON position (not starting the engine) and noticed the battery light did not come on with all the other lights. When I turn the key towards ON the battery light barely blips on then immediately turns off, so I know the battery bulb is not bad.

So since the battery light is not turning on with the key in the ON position, I believe the car is not sending a sense signal to "energize" the alternator. This is where I am stuck. I am going to try to remove the connector to the alternator and see if there is any voltage on either of the two connections on the plug.

Questions: Does anyone know which plug is the sense wire? Anyone else solved this issue? Suggestions?

Quick notes: There are no check engine codes; with the car started the battery light and brake light are not on; 120A Fusible Link has been replaced; 10A ALT fuse is good; Battery is good; Alternator has been replaced and both original and new passed alternator tests at AutoZone;

 

If the battery light was not on then you might did it for nothing.

This doesn't make sense- if the battery was fully charged this voltage would mean alt is not charging it at all so you'd get your battery light lit. How do you know your battery was fully charged?

My understanding of this is much simpler- the fully charged battery should be able to supply the car with completely dead alternator with enough electricity for about 10 minutes. Alternator has a circuit which measures voltage on the battery (thin wire coming from battery post to alternator connector) and if it notices it can't bring it up to 14.4V it lights up battery light and due to diode in the circuit- the brake light as well.

Sounds to me either battery has one cell shorted (the voltage on its posts with engine not running will be significantly less than 12.6V) or it is severely depleted or your multimeter is not telling the truth

 

I concur.

Use a different meter (or make sure it's working properly) and pull the + connector and see if the car runs fine and what the V is.

 

SOLVED: Broken wire on the plug. Fixed the wire and now everything is working properly.

Thank you Child_uv_KoRn and Max_5gen for your quick replies!

 

Makes sense- thanks for the update. I remember now I had wire fail there once- several years before some mechanic was testing the voltage and they pierced the insulation to reach to the conductor. This was in Canada at the time so few years later salt from the roads ate the conductor completely. Just make sure you insulate it well as this failure tends to happen in the winter .