car wont start and battery light on on 1999 Mercury Sable

car turns over slowly than just clicks. i tested battery with multi meter and battery tested good.

Asked by for the 1999 Mercury Sable
A multimeter is not a good enough test for a battery. A battery with standing voltage of 12.6 might show good, but as soon as a load is put on it, if it drops below 10.5, it's no good.

Your battery light -- is it on while the vehicle runs? If you can't start it, then your battery light will stay on with your other warning lights with the engine off. If you can start it with a jump and the battery light stays on - then you have a charging system failure - alternator, voltage regulator, wiring connector...

Hope this helps.