A dry van either rolls or it doesn't. A reefer can roll perfectly and still destroy its load a probe reading three degrees low, a quarter-inch door-seal gap, or a trailer that was never pre-cooled, and a full load of produce arrives at a temperature the receiver rejects on sight. Inspecting a refrigerated trailer means doing the whole standard trailer walkaround and then a second inspection on top: the refrigeration unit and the cargo space that has to keep food in the safe range the entire haul. This guide covers both layers, plus the FSMA records that prove it happened. Start free and put a reefer-specific inspection on every driver's phone.

Trailer + Reefer Unit + Cargo & FSMA

A Reefer Passes Two Inspections, Not One.

A missed belt, a drifting probe, or a skipped pre-cool doesn't show up as a breakdown — it shows up as a rejected load and an FSMA record you can't produce. Truck Inspection & Maintenance Management Software runs the reefer-specific pre-trip the same way it runs the standard one: a guided walkaround that adds the refrigeration unit and cargo-compartment checks, logs the temperature record FSMA requires, and routes any failed checkpoint straight to a graded work order before the trailer is loaded.

Start Free Trial Today Talk to Us Team
2 layersstandard trailer + refrigeration & cargo
12 monthsFSMA temperature-record retention
2–4 hrspre-cool to setpoint before loading

The Reefer Adds a Second Inspection

Everything a dry van needs — tires, brakes, lights, coupling, doors, frame — a reefer needs too. The difference is the two systems bolted on top: a diesel-powered refrigeration unit that is its own small engine, and a cargo box that has to hold a temperature for hours. A standard trailer inspection says the trailer is safe to pull. The reefer layer says the load will arrive fit to sell. Skip the second layer and the trailer can pass a roadside inspection while the cargo quietly fails.

Layer 1The standard trailer walkaround

The full 49 CFR 396.11 trailer DVIR — tires and wheel ends, brakes and air lines, lights and reflectors, suspension and frame, kingpin and landing gear, doors and latches. Same criteria as any trailer. This is the ground floor; the reefer checks sit on top of it, not instead of it.

Layer 2The refrigeration unit and cargo space

The reefer-only additions: the refrigeration unit's own fuel, fluids, belts, refrigerant and alarms; a setpoint run test that proves it cools under road load; a pre-cooled, sanitary cargo box; and the FSMA temperature record. This is what makes a reefer inspection different — and what a dry-van habit misses.

Start free and run both inspection layers in one guided flow.

The Refrigeration Unit Check

The reefer unit is a diesel engine with its own fuel tank, fluids, and belts — it ages by run-hours, not miles, and it fails the same way any engine does if no one looks. These are the checkpoints that keep it from quitting mid-haul, where "the engine shut down and the load drifted" becomes a claim instead of a repair.

Fuel levelReefer has its own 50–100 gal tank, separate from the tractor. At least ¾ for any haul over 8 hours — running dry mid-route means the box warms with no one watching.
Engine fluidsOil on the dipstick, coolant at the mark, no milky oil or discolored coolant. Exhaust clear, no excessive smoke.
BeltsTension correct, no cracking or fraying. Belts typically replaced every 1,500–3,000 engine hours — check them against the hour meter, not the calendar.
RefrigerantSight glass clear — bubbles or glazing point to a low charge or a leak. No grinding or knocking from the compressor.
Alarms & displayRun the unit's OEM self-test, clear or note alarm history, confirm the temperature display reads accurately. Door alarm triggers when tested.
Setpoint run testRun on diesel to setpoint for 15+ minutes. Shore power alone won't prove the unit cools under real road load — this does.
PM runs on hours A reefer unit's service life is measured in engine hours, not odometer miles — common PM intervals land around 250 hours for high-utilization units and 500 for average use. A trailer that looks low-mileage can be badly overdue on reefer PM, so trigger service off the hour meter and the alarm history, not the miles on the box.

Pre-Cool Before You Load — Always

A reefer is built to hold a temperature, not to pull one down. Load warm product into a warm box and you've created temperature abuse the unit will spend the whole haul failing to undo. Pre-cooling the empty trailer to setpoint — usually 2 to 4 hours ahead, with a stabilization period — is what sets the entire load's compliance chain, and it's why shippers routinely turn away trailers that haven't reached spec.

Load typeTypical setpointRun modeNotes
Frozen −10 to 0°F Continuous Run Tight tolerance, no warm-up cycles
Fresh / produce 33 to 40°F By commodity Varies: leafy greens 32–36°F
Tropical fruit 45 to 55°F By commodity Chill-sensitive — too cold damages it
Pharma / tight-tolerance Per spec Continuous Run Constant operation, no drift allowed

Setpoints vary by commodity and by the shipper's own spec — always run the load's required temperature, not a fleet default. Confirm the box has reached setpoint and held it before the first pallet goes in.

Continuous Run vs. Cycle-Sentry

The reefer runs in one of two modes, and the right one depends on the load. Picking wrong either burns fuel you didn't need to or lets the temperature drift on cargo that couldn't afford it — so the mode is part of the inspection decision, not an afterthought.

Continuous Run
  • Unit runs constantly to hold a tight temperature
  • Used for frozen, pharma, and low-tolerance loads
  • Highest fuel use — but no warm-up between cycles
  • No dependence on battery for restart
Cycle-Sentry (start/stop)
  • Unit cycles off and restarts to hold a range
  • Used for hardy, packaged, or shelf-stable loads
  • Cuts fuel use by roughly 30–50%
  • Needs a strong battery (around 12.4V+) to restart
Contact our team to set reefer run-mode and temperature fields for your loads.

The Cargo Compartment and the Probe

The box and the sensor are where small problems become spoiled loads. A tear in the air chute starves the rear of the trailer of cold air; a clogged drain pools water; a seal gap forces the unit into continuous run and spikes fuel. And the probe itself can lie — a reading 3°F below actual means a load set to 38°F is really traveling at 41°F, over the safe threshold, with the paperwork saying everything's fine.

1
Air chuteAttached, no tears, floor channels not blocked. It drives cold air to the rear — without it, the back of the load warms.
2
Door sealsLight test with doors closed. Any daylight at the corners or edges means the unit is fighting outside air all haul — a ¼" gap alone can raise fuel use 18–22%.
3
Drains & floorDrain tubes clear, floor clean with no debris, residue, or standing water. T-rail channels open for airflow under the load.
4
Defrost cycleTiming set right — too infrequent ices the coil, too frequent wastes fuel. Evaporator and condenser coils clear of debris.
5
Temperature probeCalibration within its valid period. A drifting probe is the quietest way to fail a load while the display reads perfect.

The Record Is Half the Job

With a reefer, passing the inspection and proving it are the same task — FSMA holds you to both. Truck Inspection & Maintenance Management Software captures the reefer walkaround, the sanitary cargo check with timestamped photos, and the temperature record FSMA expects, all against the specific trailer. Any failed checkpoint becomes a graded work order before loading, and the records are retained and retrievable — so when a receiver disputes a load or FDA asks, the answer is already filed, not reconstructed.

Start Free Trial Today Contact Us About FSMA Records

What FSMA Expects From the Carrier

The Sanitary Transportation rule (21 CFR Part 1) puts real documentation on the carrier, not just the shipper. None of it is exotic — it's the inspection you're already doing, written down and kept. These are the pieces an audit or a load dispute will ask for.

Temperature recordsLogged through transit at intervals appropriate to the load — commonly about every 15 minutes — with time, temperature, setpoint, and driver ID.
12-month retentionRecords and probe-calibration documentation kept for 12 months and retrievable within 24 hours of an FDA request.
Written agreementsShipper, carrier, and receiver agree in writing who owns temperature control for each load.
Sanitary conditionClean interior documented, previous load noted for allergen tracking, wash-out ticket dated and retained.

The 5-Stage Reefer Pre-Trip

Put together, the reefer pre-trip runs in a fixed sequence — pre-cool first because it takes hours, documentation last because it closes the record. Run it the same way every time and nothing in either layer gets skipped.

1
Pre-cool (2–4 hrs ahead)Bring the empty box to setpoint and let it stabilize before the shipper appointment.
2
Chassis walkaround (15–20 min)The standard 49 CFR 396.11 trailer DVIR, plus the reefer fuel check.
3
Reefer unit check (10–15 min)OEM self-test, fluids, belts, refrigerant, alarm history, hour meter against PM.
4
Cargo compartment (10–15 min)Air chute, seals, drains, defrost, probe calibration, sanitary check with photos.
5
Documentation (5–10 min)Start the FSMA temperature record, confirm calibration, complete the DVIR.
Contact support to build this 5-stage reefer flow for your fleet.

Frequently Asked Questions

How is a reefer inspection different from a regular trailer inspection?
A reefer inspection includes everything a standard trailer inspection does — tires, brakes, lights, coupling, doors, frame under 49 CFR 396.11 — and then adds two more systems: the refrigeration unit and the cargo compartment. The unit is a small diesel engine with its own fuel, fluids, belts, refrigerant, and alarms, and it needs a setpoint run test to prove it cools under road load. The cargo box needs pre-cooling, sanitary checks, air-chute and seal verification, and a calibrated temperature probe. A dry-van habit covers the first layer and misses the second — which is exactly where loads get rejected. Start free and inspect both layers in one flow.
Why does the trailer have to be pre-cooled before loading?
A reefer unit is designed to maintain a temperature, not to pull a warm load down from ambient. Loading product into a warm box creates immediate temperature abuse that the unit spends the whole haul trying — and often failing — to recover from, and the load can breach its safe range before it ever reaches the road. Pre-cooling the empty trailer to setpoint, typically 2 to 4 hours ahead with a stabilization period, sets the baseline for the entire load's compliance. It's also why shippers routinely reject trailers that show up above spec temperature.
When do I use Continuous Run versus Cycle-Sentry?
Continuous Run keeps the unit running constantly and is used for frozen, pharmaceutical, and tight-tolerance loads where any warm-up is unacceptable — it uses the most fuel but holds the steadiest temperature. Cycle-Sentry lets the unit cycle off and restart to hold a range, cutting fuel use by roughly 30–50%, and suits hardy or packaged commodities that can tolerate small swings. Cycle-Sentry depends on a healthy battery, around 12.4V or better, to restart reliably — a weak battery in that mode is a load failure waiting to happen, so battery condition is part of the mode decision.
What does FSMA require carriers to keep for refrigerated loads?
Under the Sanitary Transportation rule (21 CFR Part 1), carriers hauling temperature-controlled food maintain written temperature-control procedures, temperature records logged through transit at intervals appropriate to the load — commonly about every 15 minutes — and probe-calibration documentation. Those records are kept for 12 months and must be retrievable within 24 hours of an FDA request. There also have to be written agreements between shipper, carrier, and receiver defining who controls temperature, plus documentation of the trailer's sanitary condition. The practical takeaway: the inspection and the record are one job, because a perfect haul with no record still fails an audit.
How can a reefer pass inspection and still ruin the load?
The most common culprit is a drifting temperature probe. If the probe reads 3°F below actual, a load set to 38°F is really traveling at 41°F — above the safe threshold — while the display and the record both look fine. Other quiet failures include a torn air chute that starves the rear of the trailer of cold air, a quarter-inch door-seal gap that forces the unit into continuous run and spikes fuel use 18–22%, and a skipped pre-cool that abused the load before it ever moved. None of these stop the trailer from rolling, which is why the reefer layer of the inspection — probe calibration especially — matters as much as the mechanical one.
Unit · Cargo · Record

Inspect the Trailer, the Unit, and the Record

Truck Inspection & Maintenance Management Software runs the full reefer pre-trip in one guided flow: the standard trailer walkaround, the refrigeration-unit check, the pre-cool and cargo-compartment verification, and the FSMA temperature record — all against the specific trailer. Failed checkpoints become graded work orders before loading, PM triggers off the reefer's hour meter, and the cold-chain records stay retained and retrievable. That's how refrigerated fleets stop losing loads to a drifting probe or a skipped pre-cool — and keep every trailer both roadworthy and audit-ready.

Start Free — Run Reefer Inspections Right Contact Us About Cold-Chain Fleets
No credit card required. Free for up to 3 trucks. Built for FMCSA-compliant fleets.