2003 Taurus only starts with boost but alt and bat are good

Asked by Jan 12, 2011 at 08:33 AM about the 2003 Ford Taurus SE

Question type: Maintenance & Repair

I can only start my car with a boost.  The alt charges the battery with 12.6 volts and the battery has a full charge.  When I try to start the car without a boost, the dash lights are weak and there is clicking that comes from the relays next to the battery.  Everything will work until I try to engage the starter.  That is when the clicking starts and the dashlight go weak.  But no action from the starter.  When I attach the booster cables, everything works and the car fires up with no issues.  I can drive it and as soon as I turn it off, I need a boost to start.  Any ideas?  

1 Answer

3,695

Full charge on a 12 volt battery is actually 12.8. If your alternator is only charging at 12.6 volts it has failed. Charging voltage should be in the neighborhood of 14.5 volts and within a couple tenths of that with the heater fan on full and headlights on. Take your car to your local Advance Auto Parts and they will test the system for free.

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