AC Running But Not Cooling
Five different faults produce the same complaint. Establishing which one you have takes about two minutes, saves you a diagnostic visit, and occasionally fixes the problem outright.
Call 832-662-4107
Start here: is it running at all?
The single most useful thing you can establish before calling anyone is whether the outdoor unit is running. Go outside and look. It splits the problem in half.
| What you find | What it usually means |
|---|---|
| Outdoor fan spinning, air from vents is not cold | Refrigerant or airflow. Most commonly a frozen coil or a leak |
| Outdoor unit humming but the fan is not turning | Almost always a failed capacitor. Small part, common failure in this heat |
| Outdoor unit completely silent, nothing indoors either | Power. Breaker, float switch, or a failed contactor |
| Indoor fan running, outdoor unit dead | Contactor, capacitor or the outdoor breaker |
| Cooling but weakly, and running constantly | Low refrigerant, a dirty condenser coil, or a system undersized for the day |
The frozen coil, which is the most common of all
It sounds backwards, but ice on an air conditioner means it is not getting enough warm air across the coil, not that it is working too hard.
Restricted airflow — a blocked filter, closed vents, a failing blower — lets the coil drop below freezing. Condensation on it turns to ice. Ice blocks airflow further. Within an hour or two the coil is a block of ice and the vents blow almost nothing.
What to do: thermostat to Off, fan to On. Leave it for three to four hours. Replace the filter while you wait. If it cools normally afterwards, the filter was your problem. If it freezes again within a day, the cause is refrigerant or the blower and it needs a technician.
Do not chip at the ice and do not point a heat gun at it. Running the compressor while the coil is frozen is what turns a cheap problem into an expensive one.
Why upstairs is warm and downstairs is fine
A very common Houston complaint, and usually not a fault at all. Heat rises, attics here reach extraordinary temperatures, and ductwork running through that attic loses cooling on the way. A two-storey house on a single system will almost always run warmer upstairs.
Worth checking before assuming the system is broken: are the upstairs returns clear, is attic insulation adequate over the ceiling, and is the duct run to the far bedroom crushed or disconnected. Disconnected attic ducts are common and cost nothing to spot.
It was fine yesterday and today it is not
Sudden total loss of cooling, with no gradual decline, points at a small number of things: a tripped breaker, a failed capacitor, a full drain pan tripping the float switch, or a thermostat that has lost power or settings. All four are inexpensive.
A gradual decline over weeks points somewhere different — a slow refrigerant leak, or a condenser coil that has silted up with dust and grass clippings until it cannot shed heat.
Before you call
- Note whether the outdoor fan turns.
- Check and photograph the filter.
- Check both breakers.
- Look for ice on the copper lines at the outdoor unit.
- Note whether this came on suddenly or over weeks.
Those five answers turn a diagnostic visit into a repair visit, which usually costs you less.
Call 832-662-4107