Frigidaire Room Air Conditioner Runs but Doesn’t Cool

Fresh air is moving, the compressor may even hum, and the room still feels stale and warm. A room air conditioner cools by pulling room air across a cold coil, then pushing the heat outdoors through a second coil at the back. If either side is blocked, dirty or starved of airflow, the unit looks like it is working while the room stays warm. In San Francisco and across the Bay Area, where many people only use a unit during a short hot spell, the filter and coils have often not been touched since the last time.

Start with what you can see and feel

Put your hand in front of the supply grille. Is the air cool, or just moving? Check the sides and back of the unit as well. A unit that blows lukewarm air is trying and failing to remove heat. A unit that blows weakly may have a clogged filter or a coil covered in frost. A unit that cools for a while and then stops often freezes up and thaws, which you can confirm by looking for ice on the front coil behind the filter.

The usual suspects, in order of how often they happen

• A dirty filter. It starves the coil of air, so the coil gets too cold, freezes and stops cooling.
• Blocked airflow outside. Curtains, a shutter, a balcony frame or a wall recess that traps hot exhaust air.
• Frost on the coil. Often a symptom of the dirty filter, but it also follows low outdoor-side airflow or a stuck fan.
• A poorly sealed install. Gaps in the window panels or a sleeve that is not sealed let hot air back in.
• Wrong mode or setpoint. Fan-only, energy-saver or a set temperature above the room temperature produces fan only.
• An undersized unit. A small unit in a large or sun-facing room can only keep up so much.
• A failing compressor, capacitor or fan motor. The compressor not starting leaves the fan running with no cooling.
• A sealed-system problem. A refrigerant leak or restriction, which only a technician with the right tools can confirm.

Checks you can do in order

1. Confirm the unit is in cool mode, with the set temperature below the room temperature and the fan on a normal speed.
2. Unplug the unit and pull the front filter. If it is covered in lint or dust, rinse it, let it dry completely, and refit it.
3. With the unit still unplugged, look at the front coil. If it is covered in a layer of ice, leave the unit off with the fan running on a warm day to thaw it. Drips may come out, so put a towel under it.
4. Look outside at the back of the unit. Make sure nothing is blocking the louvers, the exhaust is clear, and the rear of the unit can breathe.
5. Check the window panels and any seal strips for gaps. Close what you find.
6. Plug the unit back in and let it run. Do one controlled power reset if the display is frozen, by unplugging for a moment and plugging back in.

Do not remove the cabinet, spray water inside the unit, bend the coil fins hard, or try to add refrigerant. If you smell burning, hear a loud grinding noise, or the cord or plug is hot, stop using the unit and switch off the outlet’s breaker. Never run a unit with a damaged cord, and don’t use an extension cord on it.

Window units, through-the-wall and portable

Installation changes the diagnosis. A window unit relies on the side panels and the sash seal to keep warm air from re-entering. A through-the-wall unit needs a proper sleeve and a clear outdoor grille, with nothing behind it recirculating hot air. A portable unit pushes heat through an exhaust hose, and a long, kinked or poorly sealed hose drags in room air and loses cooling. In each case the unit may be fine and the install is the problem. A technician looks at both.

Frost, water and noise as clues

If frost is present, the problem is airflow or refrigerant, not the thermostat. If you hear the compressor click on and off, the unit is cycling on an overload, which suggests a start component, a fan problem or very dirty coils. If the unit cools briefly and then blows warm, thaw it and recheck the filter. Water leaking into the room is a separate failure covered in our guide to a room air conditioner leaking water inside.

Why the model number matters

Frigidaire room air conditioners come in several configurations. Window and through-the-wall units such as the FHTC085WC1, FHTC125WC2 and FHWC055TF1. The label is usually on the side panel or behind the filter. The number tells the technician the unit type, so the right part and installation checks can be chosen. See the Frigidaire air conditioners guide for the lineup.

When to book

Book if the unit blows but never cools after the filter, airflow and seal checks are done, if frost returns after thawing, if the compressor does not start, or if the unit trips the breaker. For a unit that fits in a tight window or a rented flat, tell us the building type and how it is mounted. Our Frigidaire air conditioner repair visit starts with a diagnosis, and you receive a written estimate before anything is repaired, with nothing done without your approval. A sealed-system problem on an older small unit may not be worth repairing, and we say so plainly.

Frequently asked questions