Volvo Repair: Transmission?, fuse panel, storage area

Question
I just recently bought a 1990 740. The car has all service records and I think I got a good deal. The car
Will not shift into 4th gear. Other gears fine, just will not go to fourth.
Any help would be greatly appreciated

Answer
most common is a bad relay if the light stays on for overdrive I would replace the relay if it goes on and off but still not into gear it may still be a relay or a bad solenoid.the overdrive  pump relay is located on the fuse panel behind the ashtray.remove the ashtray and then remove trim around lighter socket then you will see 2 screws remove the screws and the storage area will come out the relay is white and about 1x1x3  inch.it will be towards the passengers side of the panel.