Tyler Les added 14 points and Tyrell Corbin 10 for the Aggies (5-23, 3-11 Big West), who have won four of six contests since an 18-game losing streak.
D.J. Seeley had 21 points and 10 rebounds and Isiah Umipig 15 points for the Titans (19-8, 10-4), whose six-game winning streak was snapped. Omonde Amoki blocked six shots.
Ritchart and Les made four 3-pointers each for UC Davis, which went 8 for 8 from the free-throw line in the final 1:05.
The Aggies led 72-69 when Seeley drove for a layup, and his shot was blocked by J.T. Adenrele. After gaining possession, UC Davis bled the clock down to 34 seconds before Cal State Fullerton was forced to foul.
Perry Webster had 12 points and Orane Chin 10 for the Titans.