A refrigeration unit runs while the vehicle stands: on a vehicle waiting at a dock, making a delivery or holding temperature overnight the odometer does not move but the unit hours do. A plan tied to kilometres cannot see those hours and keeps deferring service on urban vehicles.
As an example, a vehicle covering 100 km a day in the city can run its unit for 12 hours that same day, while one covering 500 km on the motorway may run it for 6. A kilometre-based plan puts the first behind the second; the real load is the reverse.
Most units carry a running-hour meter. Reading it monthly and writing it on the same line as the odometer and last service date is enough to move the plan from kilometres to hours; if hours rise on the same route, something has changed.
The calendar is a third measure: seals, belts and fluid checks age with time even if the vehicle never runs. The plan follows all three, and service happens when the first comes due; the criterion for each task is marked from the model manual.
Plan checklist:
- read the unit hour meter monthly on every vehicle
- write each service interval in the manual's criterion: hours, kilometres or calendar
- give the service company the hour record in writing
