This has been happened off and on throughout the week. The overdrive and battery light will start blinking while I'm driving. Today I decided to press overdrive to see what would happen and both the battery light and overdrive light stopped blinking.
Another thing that happens is the speedometer and rps meter will both start jolting up and down. Giving me false readings. I'm guessing that's because the battery is dying?
When I tested my battery after I pressed the overdrive button (which turned off the blinking battery light & overdrive light) My battery tested at 14 volts.

What could be the cause of this?

 

I had similar issues a while ago (flickering lights, speedo jumping around), replaced the alternator, problem solved..