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What type of alternator was put on? We have had bad luck with aftermarket alternators recently on the Taurus and have had to replace multiple units that wouldn't put out enough consistent voltage to keep the alternator light off. If you have a multi-meter you can diagnose whether the alternator is the cause:
1. Monitor the charging system voltage (preferably when the lights come on).2. If the voltage is erratic, at the alternator verify that the Orange/Light Blue (OG/LB) wire in the 2 wire connector is maintaining full battery voltage. If the voltage is not correct, check fuse #26 30A in the engine compartment fuse box. Replace the fuse if needed.3. If the fuse is OK, check for a connection or wire harness problem between the engine compartment fuse box and the alternator. Repair the OG/LB wire as needed and recheck operation.4. If the OG/LB wire maintains battery voltage, check the voltage on the output terminal of the alternator to be sure it matches the voltage at the battery. If it's different, locate and repair the voltage drop (damaged wire) in the circuit between the alternator and battery and recheck operation.5. If the wires at the alternator check OK, check the battery to be sure it's not shorted or discharged causing incorrect alternator output. Replace the battery as needed (I know you already replaced yours, but it could be an out of box failure also).6. If the battery is OK but the alternator output is not consistent, replace the alternator and recheck operation.
Let me know if you need any additional info.
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