Q: Q: Alternator not charging battery

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Hi, the problem I am having is that my alternator is not charging my battery. Battery has been load tested and checked with an ac conductance tester and it has passed both times, battery is new. Alternator has been tested twice, the most recent test was performed by a alternator rebuilding specialist on a vat40 tester, Both times it passed, voltage regulator was inspected and is in working condition. There is continuity on the battery cables from the alternator b+ terminal to the battery cable terminals in the trunk, as well as the jump posts in the engine bay. All terminal posts read battery voltage (12.6). The battery light does NOT come on when key is in on position and alternator out of car. The electrical connector that attaches to the voltage regulator shows battery voltage when probed with a multimeter and key is in on position. One of the female pins shows 10.2 volts the other 12.2. No voltage on either pin when key off. All fuses are ok. Thanks for the help!

Hi there. To be honest, when the alternator tests as good and the battery terminals are good, this issue is typically very difficult to diagnose. In most cases however, this is either an electrical relay fault to the charging system or the wiring harness from the alternator to the battery has a short. It might be helpful to have a professional mechanic come to your location to complete a battery will not hold a charge inspection.

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