Read the controller
Note the set point, the supply and return air temperatures and any alarm code. A photo of the display helps.
Repair guideARC AU 30896
Reefer container not holding temperature?
The controller is set to −20 °C but the display reads −13.6 °C and climbing, or the alarm light is on. Here’s what usually causes it, what you can safely check, and when to ring me.
Before you ring
Three safe checks
Check the power
Is the container plugged in and the supply switched on? Don’t touch a damaged plug or cable, and don’t open the control box.
Check the doors and the load
Are the doors shut and sealing? Is stock stacked above the red load line or covering the floor, so air can’t get around it?
Common causes
What I usually find
Some of these are faults in the unit. Others come down to power, loading or the doors.
Refrigerant leak
The unit runs but can’t pull the box down. The leak needs finding and repairing; topping up the gas alone only buys time.
Compressor fault
A compressor that won’t start, keeps tripping or runs without pumping properly leaves the container warming up.
Fan faults or a dirty condenser
If the evaporator fans stop, cold air doesn’t reach the load. If the condenser fan stops or the coil is clogged, the unit can’t get rid of heat.
Controller or sensor fault
A faulty sensor or controller can show the wrong temperature, run the wrong mode or keep the unit in defrost.
Power supply, plug or cable
A damaged plug or cable, a weak supply or a tripping circuit stops the unit running properly, or at all.
Airflow and loading
Reefers push cold air along the floor and up through the load. Stock above the red load line, covering the floor channels or loaded warm leaves hot spots. A reefer is built to hold product at temperature, not to cool warm stock down quickly.
On site
What it looks like
Photos from reefer callouts. Container numbers and owners’ details are blurred.
A frozen-goods container far above its set point, with the heat and defrost lights on. Ring straight away when you see this.
View larger photo ↗
If these fans stop or the coil ices up, cold air can’t reach the load.
View larger photo ↗
Gauges and recovery gear on site, so a leak gets repaired properly rather than just topped up.
View larger photo ↗When to ring
Ring straight away if…
The temperature is outside the safe range for the stock, the alarm keeps coming back, the power keeps tripping, or the unit won’t start at all.
Have the location, the brand, the set point, the temperature it’s reading and any alarm code ready. A photo of the controller and the unit’s label helps me bring the right parts.
01Should I keep restarting the unit or resetting the power?+
No. If it keeps tripping or alarming, leave it and ring me. Restarting it again and again can hide the fault and damage the compressor.
02Is a warm reefer always low on gas?+
No. Fans, sensors, the controller, the power supply and the way it’s loaded can all cause the same symptoms. It needs checking before anyone adds refrigerant.
Call James
Something stopped cooling?
Day or night, 7 days a week, anywhere in Victoria.
Call now0413 750 483 Available 24 hours · 7 days a weekWritten by James, refrigeration technician · Updated 2026-11-04