mofologic

Periodically (more often than not lately),the AC temp resets itself from 72-74 where I usually keep it to either HI or somewhere in the range of 88. I can reset it to a lower temp to engage the AC and it may or may not stay there for whatever period of time. Refrigerant charge is good and it blows cold when the temp will stay where I set it. Any BTDT ideas? Thanks in advance.....