A window AC that runs but won’t cool is usually clogged with dust or has a bad fan, capacitor or sealed-system leak. The first checks are quick and safe, and a large repair bill on an old unit is rarely a good bet. In a Tucson summer, with about 68 days a year at or above 100F, a failed window unit is a real problem, especially for renters.

What are the common problems?

  • A dirty filter. Dust chokes the airflow, so it blows weak or ices up.
  • A dirty coil. Dust and monsoon grime coat the fins and cut heat transfer.
  • A frozen coil. Poor airflow or low refrigerant freezes the evaporator. Thaw it with the fan on.
  • Fan motor or capacitor failure. The unit hums or the fan won’t spin. See AC fan motor not spinning.
  • Blocked drain. Water drips inside or outside the wrong way.
  • A sealed-system leak. Low refrigerant means weak cooling and ice.
  • A tripped breaker or bad cord. See AC tripping the breaker.

What can I check myself?

  1. Unplug the unit and clean the filter.
  2. Vacuum the front coil gently, using a soft brush.
  3. Check that the unit tilts slightly toward the outside so water drains.
  4. Make sure the seals around the window are tight.
  5. Plug it into a dedicated outlet and test.

Don’t open the sealed refrigerant system.

Is a repair worth it?

Compare the repair quote with a new unit’s price. Ask the pro whether a repair is likely to last, and be careful with an old unit. If the unit is a recurring need, a mini split or a portable unit may fit better. Some HVAC pros work mainly on central systems, so ask whether the pro works on window units.

What if I rent?

In Arizona a landlord must supply reasonable heat and cooling where such units are installed, and keep HVAC facilities in good and safe working order. In Tucson, rentals cooled by air conditioning may not exceed 82F in habitable rooms, and evaporative-cooled units 86F, per the Arizona Attorney General. A tenant-supplied window unit is a different case, so read your lease. See does a landlord have to fix AC in Arizona and window AC installation in rentals.

When the problem is bigger than one window

If the window unit is only part of the problem, and the rest of the home needs cooling, Climate Pros Tucson matches you with a licensed local pro. See AC repair and the Tucson HVAC hub. Call (520) 353-2520 and we’ll match you with a licensed local pro.