Most refrigerated loads run between 34°F and 38°F, and most frozen loads run at 0°F or lower. The number that matters is your shipper’s spec. We are Texas Reefer Solutions, and we run mobile reefer service in Dallas, TX. We set and verify trailer temperatures at truck stops and yards, not in a shop. A setpoint on its own proves nothing, so we confirm it against return air before leaving a unit. Read the bill of lading before you touch the controller. Receivers reject loads on recorded temperature.
What Temperature Your Cargo Actually Needs
Cargo type sets the number, and the spread between commodities is wider than most drivers expect. Produce that chills well sits just above freezing, while bananas and tomatoes suffer real damage at those same settings. The ranges below are the ones we see most often on loads moving through the Dallas metroplex.
| Cargo | Typical setpoint | What goes wrong outside it |
| Most fresh produce | 34°F to 38°F | Decay accelerates warm, chilling injury cold |
| Dairy and deli | 34°F to 38°F | Shortened shelf life, receiver rejection |
| Fresh meat and poultry | 28°F to 32°F | Surface freezing low, bacterial growth high |
| Frozen food | 0°F or lower | Recrystallization and freezer burn |
| Ice cream and novelties | −10°F to −20°F | Texture loss that never recovers |
| Bananas, tomatoes, squash | 50°F to 56°F | Chilling injury, blackening, failure to ripen |
Treat those as a starting point rather than an instruction. The shipper owns the spec. That spec is what a claim gets measured against, so ask for it in writing when the paperwork is vague.
Setpoint, Return Air and What the Display Is Telling You
Three numbers appear on a trailer controller and they mean different things. Setpoint is what you asked for. Return air is the air coming back off the load, and that is the reading most receivers and most download reports care about. Supply air is what the unit is pushing into the box right now. It swings low during a pulldown, which does not mean the cargo is that cold.
Product temperature is a fourth number the controller never sees. A probe pushed into a case tells you what the cargo is doing, and it lags the air by hours. When return air sits at setpoint but the load reads warm, the box is holding the air temperature it was given. That is not the temperature the product arrived at. An old fault left in the controller muddies those readings. Learning to reset a Carrier reefer unit correctly is worth ten minutes before anyone calls out.
Cool the Trailer Before the Cargo Goes In
A reefer unit is built to hold a temperature, not to pull warm freight down to one. That distinction causes more rejected loads than any controller setting. Running the box down before the doors open pulls heat out of the floor, walls and ceiling. In a Dallas, TX yard in August that stored heat is considerable.
Before a load goes on, we work through the same short sequence on every unit.
- Run the box down to setpoint and hold it there, then shut the unit off before the doors open
- Check the door seals and the air chute for gaps, tears or crushed sections
- Confirm the load is already at temperature, because a warm pallet stays warm all the way to the receiver
- Load to the return air bulkhead and keep freight off the floor drains so air can move under it
- Restart the unit once the doors are closed and watch the first pulldown before you roll
Two of those steps cost nothing and prevent most of the temperature claims we get called out on.
A unit that cannot hold its number before loading is far cheaper to sort out in the yard than on the shoulder of I-20. We schedule pre trip checks across the Dallas metroplex around dispatch, not around shop hours.
When the Box Will Not Hold Setpoint
A unit that runs continuously without reaching setpoint is telling you something specific. In Dallas heat the usual culprit is a condenser packed with road film and insects. A coil that cannot shed heat drives discharge pressure up and cooling capacity down. Pulling into shade and rinsing the coil resolves a surprising number of these.
When it does not, three suspects remain. The first is refrigerant loss. The second is a defrost cycle that never clears the evaporator. The third is a door seal letting warm air in faster than the unit can remove it. Our mobile units carry parts for Thermo King and Carrier Transicold. Most refrigerated trailer repair work finishes at the trailer rather than after a tow.
Continuous Mode Versus Start and Stop
Mode choice changes how tightly the box holds its number. Continuous run keeps the evaporator fans turning all the time. That holds temperature in a narrow band and keeps humidity steadier, at the cost of fuel. Start and stop cycling shuts the unit down at setpoint and restarts on a rise, which saves fuel and lets temperature drift.
Fresh produce and pharmaceutical freight generally belong on continuous because the airflow matters as much as the temperature. Solid frozen loads tolerate cycling because a frozen pallet carries its own thermal mass. If the shipper specifies a mode, run that mode, and note it on the paperwork.
A box that is climbing with a load on board needs a technician at the trailer, not a tow to a shop. We reach trailers across Dallas, Mesquite, Balch Springs, Forney and the I-35, I-20, I-30 and I-45 corridors. Response usually runs 45 minutes, and the price is agreed before we start. Call 214-791-3851 and tell us where you are parked.
Frequently Asked Questions
Most chilled freight runs between 34°F and 38°F and most frozen freight runs at 0°F or below, with ice cream colder still. Chill sensitive produce such as bananas and tomatoes needs 50°F to 56°F instead. The shipper’s written instruction overrides any general range, so confirm it on the bill of lading before setting the controller.
No. A transport refrigeration unit is sized to hold a load at temperature. It removes the heat that leaks in through the walls and doors. The unit cannot bring a warm pallet down within a normal transit time. Product has to arrive at temperature, and the trailer has to be cooled before loading.
A blocked condenser coil is the most common cause in Texas summer conditions, followed by refrigerant loss, a defrost fault and worn door seals. Rinsing the coil and checking the seals takes minutes. If the unit still cannot reach setpoint, it needs a diagnostic. The refrigerant your unit runs on decides who is licensed to open the system.
Setpoint is the target you programmed. Return air is the temperature of the air coming back off the load and is what most temperature recorders log. Receivers and claims adjusters generally look at return air, which is why a correct setpoint alone does not prove a load travelled in temperature.