Why does my upright freezer run constantly but it's not freezing anymore

There is probably a safety device of some description incorporated into the design though it probably isn't to blame for the trouble.

You need to discover whether it is the fan, compressor or both; neither should run constantly. The condenser fan is only needed while the compressor is pushing the refrigerant around the circuit and in many designs, where a belt driven compressor is used it is usual for the fan to be mounted on the extended motor shaft so they can't run independently.

If the compressor runs constantly and the cabinet doesn't suffer from excessive freezing it is almost certain either the compressor is failing or there is a leak and refrigerant is being lost - probably the latter.

Just had this issue. Freezer is packed usually & suspected airflow. Emptied bottom 2 shelves & vent strip was solid frost. Bottom 2 shelves were filled w/ solid roasts & other solid large items. Used blowdryer & currently waiting to see if it begins freezing top shelf.

Model Number? Sea Breeze

the freezer usually has the condensor coil sandwiched ilong the outer cabnet and in the back the lines come out in to the compressor compartment as a tech i have found the steel line rusts where the epoxy coating is no longer in tact so i would say you most likely have leaked out the refrigerant

Hi Susan Abboud - Modern freezers have increased storage capacity and keep more even temperature that may require the compressors to run longer but use less energy. Was the unit disconnected previously for any reason? If so, freezer requires a minimum of 4 hours to cold down completely. Confirm that the temperature control is not set too cold and that the door is not being open frequently. A dirty, cracked, worn or poorly fitted door gasket can allow warm air to enter the unit causing it to have to run longer to remove the warm air. Leaks in the door seal will cause freezer to run longer in order to maintain desired temperature. Cleaned the gasket, if it is too damage then it will need to be replace. You can check and see if the door seal is bad by, placing a dollar between the gasket and cabinet. Check to see if the door is being blocked by anything stopping it from closing properly. If nothing is stopping the door then replace gasket. Keep in mind that there should also be at least 4-6 in of air space on all sides of the unit. If freezer is built in or has items stored on top that cover the unit, the can cause long run times, high temperature in the freezer and premature failure to the unit. Do not block the toe grille on the lower front of the unit. Sufficient air circulation is essential for the properly operation of your freezer, about 3 inches around the unit.

Is the compressor running?

I am not an expert, but if the defrost heater is not working, then maybe when it was unpluged the coils didn't completly unthaw. If not, the freezer still will not cool properly.

This clicking noise is a bad relay.
Get it serviced before you run in to a real problem

not necessarily, is it maintaining temp? all food staying frozen? especially ice creams if stored in there. most newer freezers displace the heat generated while cooling the food through copper lines running through sides of unit, helps to cut down on air temp differences between the inside (0 degrees) and outside temp to prevent moisture and possible condensation causing premature rusting of unit

Check these two things first.  1.  Is there a thick frost buildup on the back panel at the bottom half of the freezer?  2.  Do you hear the fan running inside the freezer?  Let me know what you find.