Change your batteries in a digital thermostat. Even if it doesn’t give you the low battery signal, weak batteries can cause digital thermostats to behave erratically. Only use name brand batteries! Use the generic batteries in the kid’s toys. Cheap batteries can fluctuate voltage, confusing sensitive thermostats.
Reset your circuit breaker for the outside air conditioner. Don’t just trust the position of the handle. Firmly turn the breaker to “OFF” then “ON”. Sometimes a breaker will trip internally, without flipping the handle to the “OFF” or “TRIP” position.
Did someone get too excited with the weed-eater? Does your puppy like to chew things? Check for broken/frayed/chewed low voltage wires outside at the air conditioner. Usually there will be a big round conduit going from the house to the air conditioner, but also a smaller set of fairly thin wires ran along with it. These thin wires carry the thermostat signal to turn the air conditioner on. Dogs and trimmers love to cut and/or short them.
FILTERS! A sufficiently dirty filter can cause your evaporator coil to freeze up, sometimes suddenly. This restricts air from moving through the system. If your equipment is running, but you aren’t getting any airflow from your grills, look for ice on your copper lines. Any ice is bad, and you should shut down the system immediately. Make sure the air conditioner has been off, with the fan switch in the “on” position for at least 3 hours before a tech arrives for a freezing up problem. If the evaporator coil still has ice on it, we will not be able to fix anything and will leave and reschedule.
FILTERS! Check your air filters. Dirty filters can restrict air flow, causing a loss in capacity and efficiency. This may also lead to more severe and costly problem.
Wash your outside air conditioner. Dirt, dog hair, cottonwood, grass clippings all get sucked into the air conditioner coil. Restricting that outside air flow severely impacts how well it cools, and makes your electric bill higher. Most air conditioners can be cleaned with a water hose. Either remove the top of the air conditioner and spray from the inside out, or at a downward angle if you aren’t comfortable removing the top.
Freon: A very rough approximation of your refrigerant charge can be made by feeling the larger copper line after the unit has been running a few minutes. Generally, it should feel cool to quite cold. If it is not cool at all, the system is either low, or it is a very high efficiency coil on hot day. A HVAC tech should be the one who adjusts charge on refrigerant. Incorrectly charging your air conditioner can cause permanent damage.
Undersized: One of the more common problems, especially on older systems. The engineering specs on air conditioning systems in central Oklahoma assumes a mid 90s temperature. If it has been 100+, especially for several days, a system sized based on load calcs will lose ground. We size our systems with some extra cushion for those hot days.