There are several different things that can cause a refrigerator to run constantly including dust in the condenser coils or a broken door seal. Vacuuming the coils can resolve this issue.
Broken door seals can be diagnosed by closing the door on a piece of paper, and then trying to pull the paper out. If it is easily removed, the seal is broken. Repair or replace the door seals to reduce the amount of time a refrigerator runs.
The location and position of a refrigerator are important factors in how it will run. Make sure the refrigerator is on a level surface and away from heat sources to ensure optimal performance.