1998 Ford Taurus Why is the battery overcharging?

Yesterday, while driving, (approximately 40 mph) my car seemed to experience an electrical surge. The speakers let out a squeek and went silent. The heater and defrost fans shut off. The windshield wipers stopped working and steering became sluggish. I was in the on ramp to the freeway at the time and continued on in hopes of making it to the next exit.
The car seemed to drive "fine" but the steering was sluggish. I did get off the road and to a safe location whereupon I called AAA. They came out, cleaned the terminals on the battery and tested it. After a second cleaning and testing, the technician determined the alternator was overcharging the battery. The battery was still "good, " but providing too much charge.
The AAA Starter Test results were Voltage 10.95V, Amps, 161.1A.
The AAA Charging System Test results were No Load: 15.14V99.7A, Loaded: 14.98V, 91.3A

After driving the car for 40 minutes, I took the car to the mechanic to test, the results were as follows:
Starter Test: 11.75V, 217.3A, Loop Ohms. 11.6mΩ
Charging System: No Load: 17.79V, 91.5A, Loaded: 14.09V, 20.6A

The Mechanic says he doesn't know if it is the alternator, regulator, cables, or battery. He says he would need to do a full depth diagnostic to determine if it is the alternator or regulator before then replacing whichever is the correct part. I'm not positive, but I had thought the alternator and regulator were a combined unit in my Taurus. Either way, I decided to find another mechanic. In the meantime, my question is do the above readings mean anything and do they show an overcharging of the battery that would warrant changing the alternator/regulator assembly? Also, can someone confirm whether or not my make, model and year have a combined alternator/regulator or if they are separate entities?

I appreciate the help.