My outside A/C condenser unit will work fine in the morning and all day then around 6:00 pm the unit will just stop working and the furnace blower will run continuously. Any ideas?

How hot is the outside tempature when the unit stops working?

If the temp is in the high 90's or so it is possible that you outdoor coil is dirty and needs cleaning. You can do this yourself if you start by turning the power off to the outside unit by pulling the fuses or tripping the breaker that services only the outdoor unit.

Then take a water hose and wash the coil very good to get all of the dust, dirt, grass clipping and pet hair out of it. Let it dry for an or so and then put the fuses back in and turn it on..

If you need more information let me know and if this helps please rate my answer.

The system could also be overcharged with refrigerant.