Battery won't charge

[Lmruf1977]

About 3 months ago, my wife accidentally dropped her phone charger cable into the cigarette lighter. Ever since then, my 96 V6 standard Mustang will not stay charged. I have replaced fuses, replaced alternator, replaced battery and battery cables, and alternator wiring harness. I'm at a loss for the 1st time in my life. Need help!!!

 

[rancorkeeper]

I would suggest a voltage test to see if you have a battery drain, but since you've already started swapping out parts ... have you replaced the cigarette lighter? It could be sheer coincidence the two events happening in tandem; however, it's certainly possible a short at the lighter itself is causing a battery drain.

 

[wmburns]

"parts changing" isn't fixing this problem. Consider slowing down and test more.

What is the voltage at the battery with the motor running?

Also test for voltage at the alternator V/W wire. Use a known good ground. IF no voltage then check the ALT fuse in the engine bay.

Next confirm voltage at the large main B+ alternator terminal. Again use a known good ground.

Howto perform charging system voltage drop test
https://www.stangnet.com/mustang-fo...perform-charging-system-voltage-drop-test.56/

 

[Lmruf1977]

I would suggest a voltage test to see if you have a battery drain, but since you've already started swapping out parts ... have you replaced the cigarette lighter? It could be sheer coincidence the two events happening in tandem; however, it's certainly possible a short at the lighter itself is causing a battery drain.

I unhooked the lighter from the system and it still isn't charging

 

[Lmruf1977]

"parts changing" isn't fixing this problem. Let's slow down and test more.

What is the voltage at the battery with the motor running?

​

Also test for voltage at the alternator V/W wire. Use a known good ground. IF no voltage then check the ALT fuse in the engine bay.

Next confirm voltage at the large main B+ alternator terminal. Again use a known good ground.

Howto perform charging system voltage drop test
https://www.stangnet.com/mustang-fo...perform-charging-system-voltage-drop-test.56/

"parts changing" isn't fixing this problem. Consider slowing down and test more.

What is the voltage at the battery with the motor running?

Also test for voltage at the alternator V/W wire. Use a known good ground. IF no voltage then check the ALT fuse in the engine bay.

Next confirm voltage at the large main B+ alternator terminal. Again use a known good ground.

Howto perform charging system voltage drop test
https://www.stangnet.com/mustang-fo...perform-charging-system-voltage-drop-test.56/

All fuses are good. Voltage at alternator b+ terminal always same as battery, never over 12 volts. White/black stripe wire (exciter) only has .01 volts.

 

[wmburns]

All fuses are good. Voltage at alternator b+ terminal always same as battery, never over 12 volts. White/black stripe wire (exciter) only has .01 volts.

^^Smoking gun alert^^ With no voltage at the V/W wire the alternator's regulator will not turn on.

With no voltage at the V/W wire this means:

• Alternator fuse in the battery junction box is blown or not making good connection
• there's a wiring fault between the alternator and the BJB.
• There's a fault in the BJB such that there no voltage INTO the Alt fuse. Confirm voltage on both sides of the ALT fuse.

To double check the diagnosis use a fused jumper wire between battery positive and the V/W wire. Back probe the alternator V/W wire at the connector. What should happen next is the alternator starts putting out and the voltage at the battery to climb above 13.5 volts.

 

[I only know what I know]

^^Smoking gun alert^^ With no voltage at the V/W wire the alternator's regulator will not turn on.

Lmruf1977, No offense but I love what can be learned by topics like this, just sorry it's at your expense.

@wmburns, correct me if this is wrong but doesn't no voltage indicate a short to power instead of short to ground? I conceded to electrical problems a long time ago.