If your walk-in cooler is running but holding 45°F instead of 35°F, the refrigeration system is working but something is limiting its ability to pull the box down to temp. That’s actually a narrower problem than a complete failure, and most of the causes have a clear diagnostic path.
Here’s what you can safely look at yourself, and what to tell us when you call.
Check These First (You Can Do These Yourself)
Door gaskets and door discipline. Pull a dollar bill out of the door seam at several spots. If it slides out without resistance, the gasket is shot there. Also look for doors left ajar, damaged self-closers, or strip curtains that have lost half their strips. A warm walk-in that’s mostly cooling correctly is often just bleeding cold air constantly.
Condenser coils. If your condensing unit is outside or in a mechanical room, look at the coil fins. Heavy dust, grease buildup, or a mat of lint blocks airflow and forces the unit to work harder. A dirty condenser is one of the most common reasons a unit runs fine in winter and struggles in summer. If you see heavy buildup, note it and tell us when you call. Coil cleaning is a quick service call and often restores full capacity.
Evaporator coils and defrost. Open the panel on the evaporator fan assembly inside the cooler. If you see a solid block of ice on the coils, the defrost cycle has failed. The ice acts as insulation and the fan can’t pull air through. This is a defrost heater, timer, or thermostat issue. Not something to try to fix yourself, but worth noting before you call so the tech brings the right parts.
Fan motors. Listen. Both the evaporator fans inside the box and the condenser fans outside should be running when the compressor is on. A dead fan motor is common and the symptom is exactly this: unit runs, doesn’t cool. If you can see the fans clearly and they’re not spinning, that’s what to tell the tech.
Ambient temperature around the condensing unit. A unit mounted in a poorly ventilated space, or crammed next to a commercial oven, will struggle on a hot day. Most condensing units are rated for outdoor ambient temperatures up to around 95°F to 105°F (check the manufacturer spec plate for your unit). If the ambient temperature is near or above that range, or if the unit is exhausting hot air back into its own intake, it may never hit setpoint. Make sure the discharge side has clear airflow.
Product load and recent restocking. Did someone just load in a large delivery? A full fresh load raises internal temps and takes time to pull back down. If the unit is recovering slowly but trending in the right direction over several hours, that’s different from being stuck flat at 45°F. How long recovery takes depends on load size, unit capacity, and ambient conditions — if temps are trending down, give it time before assuming a mechanical fault.
What a Tech Will Check That You Shouldn’t Touch
Refrigerant charge. Low refrigerant (from a slow leak or normal loss over time) is a frequent cause of a unit running but not reaching setpoint. The compressor runs, the evaporator gets cold but not cold enough, and the box sits well above target. Checking refrigerant pressure requires gauges and EPA Section 608 certification. Do not try to add refrigerant yourself.
Compressor function. A compressor that’s starting to fail can run but not pump effectively. A tech will check amp draw, suction and discharge pressures, and whether the compressor is actually building pressure correctly. A weak compressor often shows up as a unit that used to cool fine but has gotten gradually worse over months.
TXV or metering device. The thermostatic expansion valve controls how much refrigerant enters the evaporator. A stuck-closed or restricted TXV causes exactly the symptom you’re seeing: the unit runs, refrigerant flow is limited, and the box won’t pull down. This requires pressure gauges to diagnose, and about two-thirds of TXVs returned as failed actually test fine, so proper diagnosis before replacing it matters.
Electrical contacts and control board. Pitted or failing contactor points can cause the compressor to start and stop erratically. A control board issue might cause the unit to short-cycle. A tech will check voltages and cycling patterns.
What to Tell the Tech When You Call
Give them this information so they come prepared:
- How long the problem has been happening and whether it started suddenly or gradually
- The current box temperature and setpoint
- Whether you see ice buildup on the evaporator
- Whether the condenser fans and evaporator fans are spinning
- The make and model of the unit (usually on a plate near the condensing unit)
- When it was last serviced
A gradual decline over weeks usually points to refrigerant leak, dirty condenser, or failing compressor. An overnight sudden change more often means a failed fan motor, defrost component, or electrical fault.
When to Call a Pro
If you’ve checked the doors, the coils aren’t obviously iced, the fans are running, and the box is still well above setpoint, you’re past the DIY checklist. The most likely causes from here (low refrigerant, compressor wear, TXV, defrost controls) all require tools and certification to diagnose properly.
If you’re holding product at questionable temps, don’t wait. The FDA Food Code sets cold holding at 41°F or below for refrigerated TCS foods. A walk-in sitting at 45°F is above that threshold and into food safety territory.
Call Bay Area Refrigeration Service. We handle walk-in repair across the Bay Area and work to get commercial clients on the schedule fast, often same or next business day when we can. The faster we get there, the better your odds of saving the product load. bayarearefrigerationservice.com