What does the check charging system mean on a ford taurus?

The check charging system light on a Ford Taurus means that the ECU has found a problem with the voltage in Your car. Your alternator should charge at 14.4 volts, and the battery should be able to rest at 12.4 volts when the car is off. If either of these are not working right then You will get a check charging system light. Usually the light will come on whenever the alternator is not working. The first thing to check on the alternator is that the belt is on it, and that the main wire on the top of it is securely attached. If all of that is okay then it may be failing. I recommend getting both a battery and an alternator test to determine which is having the problem.