Hyundai Repair: hyundai accent transmission, torque converter clutch, transmission control module

Question
When driving at highway speeds 70mph the torque converter unlocks and locks back up it sometimes happens as many as 4 or 5 times in a 15 mile trip. Drove today on the same stretch and It did not do it once. What turns the lock up off besides the brake switch.

Answer
I haven't verified this for 2006 and newer Accents, but the brake switch doesn't affect the torque converter clutch operation on 2005 and older Accents.  The torque converter clutch is controlled by the transmission control module, and it takes into account fluid temperature, throttle opening, vehicle speed, engine speed, and gear engaged (and possibly other items-- Hyundai doesn't provide information on how their logic works).  Under normal operation, the state of the torque converter clutch will vary depending on the data at that particular moment.  While your description doesn't necessarily indicate to me there's a problem, it doesn't indicate there's no problem, either.