AC Runs but Will Not Cool the House

Checks you can make first

1. Thermostat on Cool, fan on Auto, set at least three degrees below the room.
2. Go outside. Is the outdoor fan spinning and is the unit humming? If the indoor blower runs but the outdoor unit is silent, the problem is outside.
3. Pull the filter. A clogged one starves the coil of air.
4. Look at the outdoor coil for leaves, cottonwood fluff or salt crust.
5. Touch the bigger copper line at the outdoor unit. On a working system it feels cool and sweats.

What the usual causes turn out to be

• Outdoor unit off, indoor blower on. Bad capacitor, burned contactor or a tripped breaker.
• Both running, air barely cool. Low refrigerant from a leak, or a coil so dirty it cannot move heat.
• Cools in the morning, falls behind by afternoon. A unit near the end of its life, a dirty coil or one that was undersized from the start.
• Cool but damp and clammy. Blower set too fast, or a system too big for the house that never runs long enough to dry the air.

Second floors and Cape Cods

In a Cape or a split-level, the bedrooms tucked under the roof take the full summer sun on the shingles. If the upstairs stays warm while the first floor is fine, the ducts to those rooms may be undersized, leaking into the attic or crushed. A contractor can check the airflow at every register and tell you which it is.

Questions about AC Not Cooling in Middletown

How much cooler should the air at the vent be?

Supply register air usually runs 15 to 20 degrees below the temperature of the air entering the return. A smaller drop points to a problem.

Can I just top off the refrigerant?

Refrigerant is not consumed as the system runs. When it is low, it leaked out somewhere, and topping it off without finding the leak only buys a little time.