If your commercial display case is running warm, the most likely culprit is either a failed evaporator fan motor or blocked airflow around the coil. Those two causes account for the majority of calls I see on deli cases, open-air merchandisers, and bakery display units in the Bay Area. Here’s what’s actually going on and what a tech checks when they arrive.
The Most Common Causes, in Order of Likelihood
Evaporator fan motor failure. The evaporator fan pulls air across the coil and circulates cold air through the case. When that motor seizes or a blade cracks, cooling drops fast. The compressor keeps running, so the case feels like it’s trying, but product temps climb anyway. You might hear the unit running but notice it’s quieter than usual inside the cabinet.
Blocked evaporator coil (ice buildup). If the defrost system isn’t working correctly, ice builds up on the coil over time and eventually chokes off airflow entirely. This one’s sneaky because it develops gradually. You’ll often see frost or ice on the back wall or coil cover.
Condenser coil clogged with dust or grease. This is especially common in deli and bakery environments where airborne grease and flour are a fact of life. A dirty condenser can’t reject heat properly, so head pressure climbs and the system loses capacity. The condenser fan and coil are usually at the bottom front or rear of the case.
Low refrigerant. A slow leak can deplete the charge over months. You’ll typically see uneven frost patterns on the evaporator coil, reduced cooling across the case, or the compressor running longer than normal. Diagnosing this requires gauges, temperature measurements, and EPA Section 608 certification to handle refrigerant.
Failed defrost heater or defrost termination thermostat. If the heater burns out or the thermostat fails, ice builds on the coil as mentioned above. This usually shows up as a gradual cooling loss that gets worse over a few days, then partially recovers if the unit is powered off overnight. The fix means pulling the coil cover, testing the heater circuit, and replacing the faulty component.
Refrigerant metering device issue (TXV or cap tube). A restricted or failed expansion valve starves the evaporator of refrigerant. Symptoms overlap with low charge, so proper diagnosis requires gauges and temperature measurements at multiple points. Not a field repair for anyone without the right tools and training.
Door gasket failures or air curtain disruption. On reach-in cases this is obvious. On open-air merchandisers, the air curtain is doing the work of a door. If it’s disrupted by nearby fans, vents, or a duct in the wrong spot, warm ambient air pours into the case continuously.
What a Tech Actually Checks First
When a tech arrives at a warm display case, the first five minutes go like this.
Check the evaporator fan. Is it spinning? Is it pushing air? On most reach-in cases you can feel air movement at the discharge grille. No airflow is an immediate flag.
Pull the coil cover and look at the evaporator. A solid block of ice means defrost failure. Frost-free but warm means the refrigerant side needs attention.
Look at the condenser. A half-inch of grease and lint on a condenser coil in a deli case is not unusual, and it’ll tank capacity. If it’s packed with debris, that gets addressed before anything else.
Connect gauges. Suction and discharge pressures tell whether the system is charged correctly and whether the compressor is pumping. Low suction with superheat that’s too high usually points to a metering device problem or low refrigerant.
Check defrost controls. The timer or board shows when the last defrost cycle ran and whether the heater circuit is intact.
Most of the time, one of the first three checks turns up the problem.
What to Check Before You Call
A few observations you can make before picking up the phone, without touching anything inside the refrigerant circuit.
Listen for the evaporator fan. Open the case door. On most units you’ll hear the fan running. If it’s silent, note that.
Look for visible ice. Check the back wall and coil cover area. Heavy frost or a solid block of ice is worth noting for the tech.
Feel the door gaskets. Run your hand around the perimeter. Warm air leaking in is easy to feel. If a gasket is torn or pulling away, that’s likely contributing.
Check whether the condenser coil has visible debris. If it’s accessible at the front or rear of the unit, a thick mat of lint or grease on the coil face is worth mentioning to the tech. Cleaning a packed condenser requires the right tools to do it without damaging the fins.
None of these observations will fix the problem, but they give the tech a head start and help you describe what you’re seeing when you call.
When to Call Us
If the case is running but product temps are climbing, get a tech there sooner rather than later. The compressor will keep running against a bad load and that shortens its life. A case holding deli product or beverages can turn into a spoilage problem quickly.
Fan motor replacement, defrost heater swap, TXV repair, refrigerant leak diagnosis and recharge, these are all straightforward jobs if you catch them before the situation compounds. They’re not DIY territory. Refrigerant work is federally regulated, electrical diagnosis on commercial controls carries real risk, and getting it wrong typically costs more than the original repair.
We service commercial refrigeration throughout the Bay Area. Call us or book at bayarearefrigerationservice.com and we’ll get you on the schedule fast, often same or next day when we can.