Climate Gauge and Dash Temp sudden change? What's wrong??

My 2001 Passat wagon 4 motion, climate temperature gauge on both the climate control display and the dash display suddenly dropped to -44 from 71 F, then shot back up to normal, and did this twice in a matter of a few minutes. It changed the temperature of my air conditioner to heat when it went down and back to normal when it went back up. What could be going out? Is there a sensor I could change easily? Thank you!! Oh and this was the first time it did this.