An air conditioner that runs but will not cool is usually telling you about airflow or refrigerant. Both have symptoms you can read from the outside.
Know where to stop
Everything below is a check any homeowner can safely make. Anything involving opening a sealed refrigerant circuit, working inside an energized panel, or dismantling a gas train needs a licensed technician — not because we want the call, but because that is where people get hurt.
If you smell gas, leave the building and call the gas utility from outside.
Free things to try before you call
A good share of the calls we go out on turn out to be one of these. Try them first, and you may save yourself a service charge.
- 01
Check the thermostat is set to COOL and the setpoint is below room temperature — and that the fan is on AUTO rather than ON, which makes a working system feel like a broken one
- 02
Replace the air filter if it is anything other than clean; this is the single most common cause
- 03
Check the breaker for both the indoor and outdoor units — there are usually two
- 04
Check the outdoor disconnect box next to the condenser has not been switched off
- 05
Make sure every supply register is open and no furniture is blocking a return grille
- 06
Clear leaves, grass clippings and shrubs back at least two feet from the outdoor unit
- 07
Look for ice on the copper lines — if there is any, switch cooling OFF and the fan ON to thaw it
- 08
Check the condensate drain has not backed up and tripped the float switch
What it probably is
These are the most likely causes. Open one to see what it looks like and what fixing it involves.
1Low refrigerant from a leak
Refrigerant is not consumed — a system low on it has a leak. Symptoms are weak cooling that gets worse over weeks, ice on the lines, and long run times. Topping it up without finding the leak is money poured into the atmosphere; the leak needs locating and repairing.
2A dirty condenser or evaporator coil
Coils transfer heat, and a coating of dust, grass or cottonwood strangles that transfer. The system runs constantly and achieves very little. This is exactly what a maintenance visit prevents.
3A failed capacitor
This is the most common single component failure there is. A weak capacitor leaves the compressor or fan motor humming and unable to start. It is cheap and quick to replace, and it usually fails on the hottest day, because that is when the load is highest.
4A failing compressor
This is the expensive one. The signs are high amp draw, tripping breakers, or a compressor that will not start even with a good capacitor. On an older system this is usually the point where replacement makes more sense than repair, and we will show you both numbers.
5Restricted airflow inside the ductwork
Crushed flex duct, disconnected runs or too little return air can all cause it. The equipment can be perfect and still not cool the house if the air cannot get where it is going.
Common follow-ups
Why is my AC freezing up?
Either low refrigerant or restricted airflow. Both drop the coil below freezing so condensation turns to ice, which then blocks airflow further and makes it worse. Switch cooling off, run the fan to thaw it, and get it looked at — running an iced system risks the compressor.
Should I hose down the outdoor unit?
Gently rinsing debris off the outside of the fins with a garden hose is fine and helps. Do not use a pressure washer — the fins bend easily and bent fins make the problem permanently worse. Switch the power off at the disconnect first.
The AC is cooling but the house is humid.
That is usually an oversized system short-cycling — it hits the setpoint too fast to remove moisture. Correct sizing is the real fix; a whole-house dehumidifier is the retrofit answer.
Prefer to call?
(423) 357-1922- Office hours
- Monday to Friday, 8–5
- Outside those hours
- Emergency service is available — call the same number.
- Where we go
- Church Hill, Kingsport, Mount Carmel, Surgoinsville, Rogersville, Johnson City, Bristol, Greeneville, Morristown and across into Southwest Virginia. Full service area.
- Where we are
- 119 E Main St, Church Hill, TN 37642
Still not working after these checks?
That is what we are here for, and emergency service is available.
(423) 357-1922