Why this index exists
Most refrigeration websites give you a phone number and a stock photo. That is not useful at seven on a Saturday evening when a box is climbing through 48°F and there is forty thousand dollars of product inside it. What is useful is knowing whether you are looking at a five-minute fix, a part that has to be ordered, or a system that is about to need replacing.
So we wrote out the symptoms. Thirty of them, grouped the way a technician actually thinks about them — not by equipment brand, but by what the box is doing wrong. Each page names the causes in the order we find them in the field, tells you what to check before you call anybody, and says plainly when it is past the point of checking.
Some of these you will solve yourself in ten minutes. We are fine with that. The operators who understand their equipment are the ones who end up on a maintenance contract, and those are the customers worth having.
Temperature — the box is not holding
Ice and frost where it should not be
Defrost faults
Water in the wrong place
Doors
Electrical and controls
Refrigerant and compressor
Noise and smell
The three things worth knowing before you read any of these
- Write the temperature down before you touch anything. Box temperature, and if you can get it, the discharge air off the evaporator and the return air going into it. The split between those two numbers tells a technician more in ten seconds than twenty minutes of description.
- Note what changed. New product load, a delivery that held the door open, a cleaning crew who hosed the floor, a power blip, a cold snap. Refrigeration faults are rarely spontaneous. Something almost always moved first.
- Photograph the coil. One picture of the evaporator with the fan guard off eliminates half the possible causes before anyone drives out. If there is ice, where the ice sits is the diagnosis.
When to stop reading and call
Three situations are not worth diagnosing yourself. If product is above 41°F and climbing, you are on a clock the Massachusetts Retail Food Code sets, not one you set. If you can smell refrigerant or hear a hiss at the coil, you have a leak and under the EPA rules that took effect in January 2026 it has to be logged and repaired, not topped up. And if a breaker has tripped twice, stop resetting it — the third reset is how a compressor becomes a replacement instead of a repair.