What are the three buttons W,Eand S for next to the gear shifter

W=winter. S=Sport. E=economy.

W=winter or wet weather.

Go to URL Below for the arrow instructions and repair.

http://www.justanswer.com/volvo/2w2j9-1998-volvo-s90-arrow-instrument-cluster-flashing-transmission.html

If your having issues with selecting the mode you want W, E or S mode then the arrow blinks and is likely the gear position sensor.

Eco, Winter, and Sport modes. The eco and sport modes change shifting characteristics more towards economy or performance, as implied. Both are suitable for everyday driving. Winter/Wet mode starts the transmission in higher gear in order to get traction to get the car going. When you turn this mode on, an up arrow light will turn on on the dash. Only use this mode when absolutely necessary, as it it harder on the transmission.

The arrow light flashing means there is a fault in the automatic transmission. Try rowing through all the gears a couple times fast, and see if it goes away. It could be the park neutral position switch. Otherwise, get it scanned.