Rooftop HVAC Unit Running But Not Cooling: What It Usually Is

The Facts

Rooftop Unit Not Cooling

What It Usually Is

Run capacitor failed: the outdoor fan or compressor hums but will not start. The most common single part we replace.
Drain safety (float) switch tripped from a clogged condensate drain: the unit shuts off cooling to protect the ceiling. On some brands this shows as a drain code.
Condenser coil dirty or blocked: head pressure climbs and the unit trips on high pressure, especially in the afternoon.
Low refrigerant from a leak: cools slowly, coil ices, never reaches setpoint.
Contactor, fan motor, or high-pressure switch failed.
Thermostat mounted somewhere it reads wrong, like above a heat lamp or on a sunny wall, so the unit is doing exactly what it is told.

Check This First

Is the outdoor fan turning? Is the compressor running, humming, or silent?
Is there water in the drain pan or a float switch tripped? Any drain code on the thermostat or board?
Is the condenser coil visibly dirty?
Where is the thermostat, and what does a second thermometer in the room say?
Text a photo of the rooftop unit's nameplate and the thermostat screen to 601-337-1069.

When To Call

The room is above 78°F and climbing with the unit running.
The unit cycles on and off every few minutes.
You hear a hum or click outside but the fan is still.

What the Repair Usually Costs

Capacitors, contactors, and drain clears are the low end of the rooftop range. Fan motors and pressure switches are mid-range. Leaks depend on location, and compressors and boards are the complex end. Ranges from our own invoices are on the rooftop unit repair cost page.

The diagnostic visit turns that range into a number for your unit, and you approve the number before any repair happens.

Rooftop

Need the Documents Today?

Text 601-337-1069 with the certificate holder's legal name and address, or email the vendor form. The W-9 and certificate of insurance come back the same business day.

Text the Request

Common Questions

Rooftop Unit Not Cooling FAQ

Can I reset it myself?

Turning the unit off for a few minutes and back on clears a high-pressure trip once. If it trips again, the cause is still there, usually a dirty coil or a failing fan motor.

Why does it only fail in the afternoon?

Head pressure rises with outdoor temperature. A coil that is marginal at 85°F trips at 95°F. A coil cleaning usually fixes it.

Do you service package units over restaurants and stores?

Yes. Rooftop package units over kitchens, dining rooms, and retail are a large share of our HVAC work, from our own bucket truck.

Rooftop Unit Running But the Room Is Hot