The build date alone does not establish the condition of refrigerated-body insulation. Panel damage, seals, joints, later-drilled holes, refrigeration equipment, route and measurement arrangements can point to different causes. Compare these inspection and operating records together before assigning a symptom to insulation failure.
Shell and sealing signs
Inspect inner tears, swelling, impact marks, open panel joints and holes drilled after delivery. Check seal compression, door alignment, latches and continuous contact around the perimeter. Moisture does not establish that an entire panel is irreparable; identify its location, spread and panel construction before deciding on replacement.
Separate the unit from the body
A longer pull-down or higher running time can come from the panel and seals, but also from the gas circuit, compressor, defrost, airflow, setpoint, product load or sensor position. The Thermo King Precedent manual is a model-specific example that treats unit operation separately from body/insulation, door and seal checks (Thermo King Precedent operator manual).
| Symptom | Alternative causes | Next check |
|---|---|---|
| Pull-down takes longer | Unit service, load, setpoint, panel, seal | Trend under same empty-body/ambient conditions and unit service record |
| Running time rises | Hot weather, door openings, route, product heat load | Separate route, doors, product start and unit data |
| Inner surface swells or tears | Impact, moisture, joint or panel damage | Inspect location, spread and panel layers |
| Suspected door leak | Seal, alignment, latch, door geometry | Perimeter check and door-adjustment record |
| Logger graph fluctuates | Sensor position, airflow, door, unit | Compare sensor calibration/position with door and unit events |
Make the field trend comparable
A useful comparison records ambient and body starting temperature, setpoint, power mode, door openings, load and sensor position. In a hypothetical comparison, a warmer starting body can take longer to cool even if its insulation is unchanged. Comparable trends help identify when to investigate; they are not a K measurement or a diagnosis on their own.
Record repair and recheck
The repair report should state exact location, damage type, method and material, date, photos, inspector and any changed sensor, seal or door setting. Confirm the scope and result of any required retest with the manufacturer or competent body. Keep the body's use, vehicle load and route conditions in the handover file.
An annual inspection list should not trigger automatic replacement by age: review inner surfaces and joints, doors and seals, holes and fittings, unit service history, route/door pattern and logger position together. Keeping findings in one format makes the next field inspection genuinely comparable.
Send current body photos, previous repairs, unit service history and comparable temperature records with a service request. Distinguishing what K measures from what a field symptom shows helps avoid work on the wrong component.
