Originally Posted by WALT

Dont know what year your working with but unlike most cars that have a vacuum booster and standard brake master cylinder --these babys have an electric hydraulic brake pump and master that is part of the anti lock system -- Fluid contamination is always a good place to start but there are many things like low fluid level or imbalance in braking pressures / brake pump or pressure switch that can cause the light to come on -- You have to describe the sequence that this problem occurs -- is the car ok initially then gets worse when your driving or is it
bad in the driveway ??? --- does the light only come on when you are depressing the pedal or is it on all the time -- is the anti-lock light on at the same time or is it delayed -- The Anti-lock will come on as a response to a brake system problem even if there is nothinhg wrong with the antilock system itself -- the HARD PEDAL is what
we really need to focus on here and that can be the result of the Pump not running
--accumulator or pump pressure switch not working correctly or the more off chance that the anti-lock control valve is not porting pressure to the wheels-- There is also a brake pump relay in a cover right next to the master on the firewall that can be bad ( they fail on a regular basis ) If you run the tests on the relay and it is bad make sure that you only buy one from the Ford dealer -- Each one is unique and
the parts stores do not have them right --- ( major past experience problems)
There is a test connector in the trunk that you can plug an analyzer into
for the anti-lock system for fault codes -- Having the proper equipment and
the manuals for this system is almost mandatory for any kind
of troubleshooting --
I can send you the diagnostic pages if I know what year / model your working with
Happy Hunting
Walt