By Commercial Service Company · September 26, 2026
When a commercial HVAC system won't keep a building cool, it's rarely one dramatic failure. Most of the time it's one of a handful of common culprits: restricted airflow, low refrigerant charge, a worn contactor, a miscalibrated thermostat, or an unbalanced zoning system. Before you assume the whole unit is shot, it's worth working through these in order — it can save you an emergency service call, or at least help you describe the problem accurately when you do call.
Check Airflow First
Airflow problems are the most common reason a commercial system runs but doesn't cool. If the coil can't move enough air across it, the space won't drop in temperature even though the compressor is working fine.
- Dirty or clogged air filters, especially in restaurants and kitchens where grease and grease-laden vapor build up fast
- Blocked or dirty condenser coils outside, often packed with cottonwood, grass clippings, or dust
- Closed, blocked, or disconnected supply and return vents inside the building
- Failing or slipping blower belts and motors that can't move rated air volume
Walk the space and check supply registers for weak airflow, and look at outdoor units for visibly dirty coils or debris packed against the cabinet. These are things staff can often spot without any special tools, even if the repair itself needs a technician.
Refrigerant Charge Problems Need a Licensed Technician
If airflow looks fine but the air coming out of the vents isn't cold, refrigerant charge is a common next suspect. A system that's low on refrigerant — usually from a slow leak somewhere in the line set or coil — will run longer, cool less, and can eventually damage the compressor if it's left alone.
This is not a DIY area. Refrigerant work requires EPA certification, proper recovery equipment, and leak detection to find the actual source of the problem instead of just topping off a system that will leak right back down. If you suspect low charge — ice forming on the indoor coil or lines, weak cooling despite good airflow, or a compressor that runs constantly — that's a call for a licensed technician, not a guess-and-check job.
Bad Contactors and Electrical Components
The contactor is the relay that switches power to the compressor and outdoor fan. Contactors take a beating from constant cycling, heat, and, in Arkansas, humidity — and the contacts eventually pit, burn, or stick.
- A unit that hums but the outdoor fan and compressor never start can point to a failed contactor
- A stuck-closed contactor can keep a compressor running even when the thermostat is satisfied
- Chattering or buzzing at the outdoor unit is a common sign a contactor is on its way out
Contactors are inexpensive to replace, but they involve line-voltage electrical work inside a disconnected panel. Any diagnosis or repair involving electrical components should be handled by a licensed technician — not tested with a multimeter by someone unfamiliar with the equipment.
Thermostat and Control Issues
Sometimes the equipment is working correctly and the problem is what's telling it what to do. On commercial systems, this shows up a few common ways:
- A thermostat or building automation sensor reading the wrong temperature because of its location — near a door, a kitchen line, or direct sunlight
- Programming set incorrectly after a schedule change, staff turnover, or a power outage that reset settings
- Aging thermostats or sensors that have simply drifted out of calibration
- Multiple thermostats on one system fighting each other's calls for cooling
Before assuming the equipment has failed, it's worth confirming the thermostat setpoint, mode, and schedule are actually set the way you expect. A five-minute check here occasionally solves what looks like a major mechanical problem.
Zoning Imbalances
Buildings with multiple zones — a dining room and kitchen on separate zones, or different tenant spaces on one rooftop unit — can develop imbalances where one zone stays cool and another never catches up. This usually comes down to dampers stuck open or closed, a zone control board issue, or ductwork that wasn't balanced correctly for how the space is actually used today versus when it was installed.
If one area of the building consistently runs warm while the rest cools fine, that's a zoning and airflow-balance issue more than a whole-system failure, and it's worth mentioning specifically when you call for service so the technician can start there.
When to Call a Professional
Basic checks — filters, vents, obvious debris around the outdoor unit, and thermostat settings — are reasonable for building staff to look at. Anything involving refrigerant, electrical components, compressors, or gas should be left to a licensed technician. Working on those systems without the right training, tools, and certification is a safety risk to your staff and can void equipment warranties.
If your building's commercial HVAC system isn't keeping up, Commercial Service Company has been servicing restaurants, grocery stores, and commercial facilities across Conway, Little Rock, Benton, Bryant, Maumelle, Jacksonville, Searcy, Russellville, and the rest of central Arkansas since 1976. Call us at 501-548-2374 and we'll get a technician out to find the actual cause instead of guessing.