Solved 2005 Explorer Alternator Wiring.

[tcarney57]

My 2005 V6 flex 4WD Explorer is throwing a Check Charging System message on the dashboard. Fully-charged (separate charger) battery reads 12.4V. So does the main B+ post on the alternator. With engine running the battery reads 11.2V. I'm trying to verify wiring, fuses, fusible links before replacing alternator.

The Haynes manual diagram does not seem to match my alternator. It (my alternator) has the main B+ post, a separate blade-type connection nearby with a ~12-gauge white/black wire, and a three-wire connector on the right-hand side. I am assuming the separate black/white wire near the B+ is the alternator field wire, and that it ought to read the same as the battery voltage with the engine off. Instead, it reads 0V (not even any random millivolts--as if it were grounded). Is my assumption correct, and that there's something wrong with the field wire connection back to the battery?

Thanks,

Todd

 

[Motorhogman]

Not sure about your wiring question. But, at 12.4 V your battery is not fully charged. More like 50% charged.

 

[BrooklynBay]

Check the high current fuse on that circuit.

 

[Number4]

Checking the voltage at the battery is just a surface charge. You need a load tester to test it.

I had an issue with the connector at the alternator. It was loose on the pin that talks to the computer. This caused a bad signal to the PCM which resulted in the computer not telling the alternator to charge.

I spliced in a new connector and all has been good since. Previously, when I’d jiggle the connector, it would work for a while.

 

[tcarney57]

iMy 2005 V6 flex 4WD Explorer is throwing a Check Charging System message on the dashboard. Fully-charged (separate charger) battery reads 12.4V. So does the main B+ post on the alternator. With engine running the battery reads 11.2V. I'm trying to verify wiring, fuses, fusible links before replacing alternator.

The Haynes manual diagram does not seem to match my alternator. It (my alternator) has the main B+ post, a separate blade-type connection nearby with a ~12-gauge white/black wire, and a three-wire connector on the right-hand side. I am assuming the separate black/white wire near the B+ is the alternator field wire, and that it ought to read the same as the battery voltage with the engine off. Instead, it reads 0V (not even any random millivolts--as if it were grounded). Is my assumption correct, and that there's something wrong with the field wire connection back to the battery?

Thanks,

Todd

Many thanks for everyone's input. The white/black wire does not feed battery power to the field coils. It's a connection back to the stator that in higher-output alternators is internal. [EDIT: With the engine running, this wire should have about one-half the battery voltage. Mine measured 0V without any floating digits--that is, dead zero, as if the connection was grounded. That meant there was an internal fault in the built-in regulator unit.] The excitation power comes in on the three-wire connector and was present when I back-probed it. I've replaced the alternator and the problem is fixed. Thanks again. --Todd

 

[BrooklynBay]

Thanks for the update. Your thread is now marked as being solved.