I had this same problem with my 85 245 wagon--the up arrow was indicating a problem with the overdrive relay--at first I guessed it was merely the light that was the trouble, because tapping the dash made it go out. A simple fix,it seemed, but when I looked further into it, I found out that tapping the dash was moving the relay, thus the light would go out. It's a pretty simple fix via removing the glove compartment, and the relay cost around 30-50 dollars, depending on your access to parts.