Question about 2003 Ford Focus

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Replace battery and two alternators, battery light still comes on at certain rpms. Could I have the wrong battery?

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Try replacing your Belt tensioner and the Serpetine belt. When your A/C clutch cycles the tension changes and your belt is slipping on the Alternator pulley. The A/C compressor will turn off on heavy acceleration to boost speed.

This could explain the light coming on at certain speeds. The modern Alternators contain Voltage Regulators. The Regulator would be the only other part that could cause your problem. Since you replaced the Alternator, it would contain another Regulator.

Make sure the Battery cables are clean and tight. Put both the Tensioner and Belt on as a pair this time. This will insure the tightest fit possible.

As long as you put in a 12 Volt battery connected to the correct terminals, there is little you could do wrong with the battery.

I hope you are happy with my reply and Thank You for using Fixya!

Posted on Sep 08, 2010


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