Question about 2003 Ford Windstar

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2003 windstar alternator over charge I try 5 or 6 alternator diferent companie always the same problem go up to 18.80 v help me please

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It should notgo over 14 1/2 volts.

Get free DTC codes scan from Autozone. I think you will get DTC code 1246 - System Voltage Malfuction.

The I (indicator) (BAT light) wire activates alternator field circuit.

The heavy B wire circuit sends current to the battery for charing and to run the car.

The S circuit helps control the amount of charge. I suspect yours is not controlling. This car has the PCM (engine computer) help control the output and turn the BAT light on when under or over charging.

SECTION 414-00: Charging System - General Information 2003 Windstar Workshop Manual
DESCRIPTION AND OPERATION Charging System This vehicle is equipped with a powertrain control module (PCM)-controlled "smart charge" charging system. The PCM-controlled charging system is a system whereby the PCM determines the optimal voltage setpoint for the charging system and communicates this information to the voltage regulator. The PCM-controlled charging system is unique in that it has two uni-directional communication lines between the PCM and the generator/regulator. Both of these communication lines are pulse-width modulated. The GEN COM line communicates the desired setpoint from the PCM to the voltage regulator and the GEN MON line communicates the alternator load condition to the PCM. The third pin on the voltage regulator, the A circuit pin, is a dedicated battery voltage sense line.

  • Charging system malfunction (high or low system voltage)
  • possible causes:
    • A circuit 35 (OG/LB).
    • A circuit fuse link.
    • B+ circuit 36 (YE/WH).
    • B+ circuit fuse links.
    • Generator.
    • PCM
    • GEN-COM circuit 586 (RD/PK).
    • GEN-MON circuit 585 (VT).
    Generator The generator (10300) on this vehicle is monitored and controlled by the powertrain control module (PCM). The PCM monitors the voltage regulator and sends a duty cycle command back to the voltage regulator to regulate the amount of field current supplied to the generator. The generator has an internal voltage regulator. The generator and voltage regulator are installed as an assembly.
    I'll send wiring diagram tomorrow.

    please rate

    Posted on May 20, 2011

    • gerry bissi May 20, 2011

      The PCM (powertrain Control Module) controls the out put of the alternator (generator). However, I must add that only 1 in 10,000 is ever bad. So, it is likely a wring issue in the circuit to or from the PCM to alternator. Check the wiring first for open circutis, frayed, or loose pins in the connector.

      Look very closely at the alternator connector, the wiring for damage and the terminal pins for looseness, spreading, corrosion. The Red/Pink stripe and the violet wire. report results.

    • gerry bissi May 26, 2011

      great job finding the bad wire. Many techs have a hard time finding bad wires.


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    I am having the same problem since i replaced the alternator 2 years ago, the battery light has always been on but everything seens ok even wen i went to the mechanic today i was working in the car i didnt touch any elctrical that could affect the alternator and when i was driving my the needles and ODO in the cluster get to the top, like whem you first turn the key to ACC, I have discover that this happens exactly when the alternator sends above 15 volts to the B+ terminal, i will check continuity in the cables tomorrow but it seens like the PCM that controls the alternator is sending a high field current that could be the reason why the voltage is almost 18V

    Posted on May 06, 2013

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    Computer controls voltage output of alternator

    Posted on May 20, 2011

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