03 ford focus replaced alternator checked charging system still not charging have power to alternator from battery light comes on after 10 seconds while running new battery, it only shows battery voltage on tester?????

When the battery light comes on it is telling you that there is a problem in the charging system. Have the charging system checked by a mechanic. Most likely the alternator is starting to fail.

Did you have the charging system diagnosed or did you just guess at it being the alternator . The charging system is computer controlled . The starter isn't working because low power , battery dead . Is there B+ voltage at the wire on the back of the alternator .B+ voltage at pin 3 at the connector pluged into the alternator .
Charge the battery use a volt meter an test for B+ voltage at the places i mention . No check engine light ? DTC'S - diagnostic trouble codes stored .
Ford Smart Charge System Alternator Not Charging
Ford PCM controlled alternator testing

(this damages the ecu Disconnected negative terminal and car still ran) check and clean the alternator connections. and check the earths. light can come on if water has gotten into the alternator or the connection has come loose. you don't disconnect the battery when the engine is running as it can shock the ecu alternators have a built in voltage stabilizer but this only works with feed back from the battery no feed back it can convert ac instead of dc and blow up the ecu. it also damage other parts.

Go through few Alternator related solved Solutions including replacement of alternator.Select and Click the link below:----How to replace alternator? http://schematicsdiagram.blogspot.com/2011/12/how-to-replace-alternator-on-gmc-sonoma.html
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How to test alternator on Dodge Stratus?

http://technoanswers.blogspot.in/2012/02/how-to-test-alternator-on-dodge-stratus.html

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How to test and replace Alternator on Audi A4 Car models?

http://repairhelpcenter.blogspot.com/2011/11/how-to-test-and-replace-alternator-on.html

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How to Remove Voltage Regulator on Car?

http://vwrepairhelp.blogspot.com/2011/11/how-to-remove-voltage-regulator-on-car.html

HOW TO REPLACE AN ALTERNATOR BELT

http://schematicsdiagram.blogspot.com/2011/08/how-to-replace-alternator-belt.html

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How to monitor Vehicles charging system? http://repairhelpcenter.blogspot.com/2011/11/how-to-monitor-vehicles-charging-system.html

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Car Alternator making noise? http://repairhelpcenter.blogspot.com/2011/11/car-alternator-making-noise.html

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After replacing Alternator, the battery indicator light Comes ON dash?

http://howtobyme.blogspot.com/2011/11/after-replacing-alternatorthe-battery.html

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How to inspect Vehicles Alternator?

http://repairhelpcenter.blogspot.com/2011/11/how-to-inspect-vehicles-alternator.html

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How to Test Vehicles Alternator?

http://repairhelpcenter.blogspot.com/2011/11/how-to-test-vehicles-alternator.html

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How to Service Vehicles Alternator?

http://repairhelpcenter.blogspot.com/2011/11/how-to-service-vehicles-alternator.html

How to Replace Alternator? http://repairhelpcenter.blogspot.com/2011/11/how-to-replace-alternator.html

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Alternator testing? http://schematicsdiagram.blogspot.com/2011/12/alternator-testing.html--------- Cars electrical system is pulsating? http://technoanswers.blogspot.in/2012/01/cars-electrical-system-is-pulsating.html------ 1998 Ford F150 pickup Battery Drains overnight due to Alternator? Alternator drains car battery? http://technoanswers.blogspot.in/2012/02/1998-ford-f150-pickup-battery-drains.html------- 2002 Ford Focus sits over night and battery goes dead? http://technoanswers.blogspot.in/2012/02/2002-ford-focus-sits-over-night-and.html--------- Charging system problem on Chrysler LHS car? http://technoanswers.blogspot.in/2012/02/charging-system-problem-on-chrysler-lhs.html---------- How to replace alternator 1997 Dodge Stratus? http://technoanswers.blogspot.in/2012/02/how-to-replace-alternator-1997-dodge.html------- How to replace Alternator on Mitsubishi Lancer http://www.howtorepairguide.com/2012/10/how-to-replace-alternator-on-mitsubishi.html
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These details will help.
For more help.Keep updated.
Thanks.
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You may have a a/c voltage leak comming from the alternator..If its a rebuilt alternator sometimes you get a bad one ..But make sure all your connections are good ecspecially the small wires coming out the back ..These are the field and sensor wires..Plus make sure all your grounds on the vehicle are not broken or missing..You can have good voltage but it may have a drop going to the computer because of a ground and cause the light to come on

need to find out if your battery is charged charge your battery and try again

Disconnect battery ground for 30 seconds & reconnect. Light should be out unless you have deeper diagnostic problem. Charging system good Battery good. This action should reset trouble light. Good luck!

Battery light is a signal from the alternator that charge is below a given voltage , check charging system.

This may indicate a problem with the battery or in the charging system. Take the car to an autoparts store and have them check the battery and alternator output. Most parts stores offer this service at no charge. Hope this helped and best wishes.

yes the alternator has failed or the wiring to it, this caused a low voltage condition that caused the engine to stop once it went below about 10 volts.