Battery won't charge

Lmruf1977 · Apr 24, 2018

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 · Apr 24, 2018

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 · Apr 24, 2018

"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 · Apr 24, 2018

rancorkeeper said:
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 · Apr 24, 2018

wmburns said:
"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/

wmburns said:
"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 · Apr 25, 2018

Lmruf1977 said:
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 · Apr 27, 2018

wmburns said:
^^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.

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