Question about 2005 Ford Mustang

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Check Charging System Light comes on ~1 minute after starting car

2005 Mustang 4.0 L V6. Battery was not charging checked with voltmeter with load on electrical system and measured 10 VDC and falling quickly. Replaced alternator with unit from Ford dealer (Motorcraft remanufactured.) Opposite problem occurred. Charging rate went to 18 - 20VDC with load & engine rev. Boiled acid & battery and acid came out weep holes. Replaced battery and another reman alternator (this time from O'Reilly as Ford did not have another in stock) Alternator charges and voltage regulator seems to workfine. 12.5VDC idling & spikes to ~ 14VDC with rev before regulator returns it to ~12.5 - 13VDC. New problem is that "Check Charging Syetem" warning and battery icon now come on approx 1 minute after starting car.and will not go off until car restart and in approx 1 minute comes on again. Alternator is charging the battery fine, everything works. Did the Ford alternator fry smething at 18-20VDC? If so, what? What waits approx 1 minute to register a chargng fault?

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Hello sir we have read your problem at fix ya!.let me come to your problems one by one according to your statements.your first replacement of the battery is correct.the battery dies usually when its used over and over. but i am not sure why you replaced your alternator as the second option.did you check whether the car runs fine after changing the battery alone.any way, after replacing the alternator for the second time you said the charging voltage is 12.5 - 13 v dc. thats a normal voltage.but since you have specified that a warning is issued on "charging system ", i advise you to check the whole electrical system again.the fact that why i say this is since the second alternator gave a voltage of about 18v, there are possibilities for the inbuilt voltage sensors and relays to get damaged following such high voltage.generally the fuses and relays will be built in that withstand only an extra 25% of the prescribed voltage, but the voltage that was generated is more than this. so please check not only the sensors and relays in the electrical system, but also whole system for any damage, since it is the battery which supplies power to all parts. thanks for using fixya! and please dont forget to rate my solution.

Posted on May 31, 2009


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