If you can't see any mechanical or cleaning issues, contact an HVAC professional. Broken thermostat: A faulty or broken thermostat is a common cause of a frozen AC.
Yes, a thermostat can cause your AC to freeze. But there are a few other things that can cause the same problem; dirty air filter, low refrigerant charge, condensate drain clogged, indoor blower not running, thermostat temperature set too low.
A bad thermostat can be detected when your AC or furnace is not turning on, your HVAC systems are not turning off, the thermostat not responding, your HVAC system is short-cycling, the room temperature not matching the temperature displayed on the thermostat, and the programmed setting resetting themselves.
Improper Freon Levels – If your system is too low or too high on Freon (refrigerant), it could cause the temperature of your evaporator to drop, freezing moisture and thus icing up the system. This could be due to a Freon/refrigerant leak that a contractor will need to repair.
AC Refuses to Start or Stops Suddenly: A thermostat that's not working correctly might fail to initiate the cooling cycle or might randomly shut off the AC. This erratic behavior can be due to electrical issues or miscommunication with the AC unit.
Any time you are having an issue with heating and cooling units, such as after a sudden power failure or after your children have had 'control' of the system while you've been away, resetting the thermostat should be the first thing you try when attempting to rectify HVAC system issues.
If the thermostat fails, you're going to be in trouble. The coolant trapped in the engine will get boiling hot, while the coolant in the rest of the system remains stone cold.
1st Step: Turn Your HVAC Unit Off.
Even if it's sweltering outside, you still need to turn OFF your air conditioner! Running a frozen air conditioner will wear out parts much faster, and could overheat your unit. Worn parts are bad news for the most expensive piece of your HVAC unit—the compressor.
Turn the AC off, it will eventually thaw itself. Leaving the indoor fan running to help blow warm inside air over the coil helps this happen faster.
LOW REFRIGERANT
Improper refrigerant fluid levels can also cause an HVAC unit to freeze up. When the refrigerant is low, the coils will be too cold, causing them to freeze. You can hire air conditioning service and repair to check your refrigerant levels and replace them, if necessary.
A malfunctioning thermostat has a harder time maintaining a setting, and may quickly shift temperature settings with no warning. If your central air has a difficult time maintaining the set temperature, even after lowering a setting for a test trial, it could be the thermostat.
Replacing a Thermostat. You'll pay between $15 and $300 for the unit in addition to labor ($65 to $100 per hour) to replace an old thermostat with a new one. However, installing a brand-new thermostat is more involved and, therefore, more expensive.
You, Will, Have a Significant Repair Bill to Pay
Not only can it damage that specific component, but other adjoining components as well, and can lead to a compressor failure! You can end up replacing several other parts of your system because of the frozen evaporator coil.
Air conditioners are designed to function in a specific temperature range. If you are running your air conditioner when the outside air is below 62 degrees, then the pressure inside your system will drop, and this can cause your air conditioner to freeze up.
Well, the thawing process could take up to 24 hours depending on the size of your unit, the extent of the ice buildup, and the efficiency of your blower fan. If the freezing on your air conditioner was just starting, it could clear up faster in an hour or two.
To check if your air conditioning unit has frozen coils, watch out for the following telltale signs: The cooling unit runs continuously but fails to cool your home effectively. Instead of cold air, you notice warm air blowing from the vents.
Then, change the fan setting from 'auto' to 'on. ' The fan will slowly defrost the system. Once your air conditioner is ice-free, you can turn it back on and reset the fan to auto (This may take an hour or more).
Turn the Thermostat Fan Setting to On. Turn your thermostat fan setting to “On” so that the fan continues to blow air over the coil. The warm air in the home will naturally defrost the frozen coil. In severe cases, the heat can be turned on to speed up the process.
To defrost your HVAC unit, you want to begin by turning off your thermostat and turning your fan on. Let the fan run over the next few hours to allow your unit to defrost.
When the filter becomes dirty, this can block airflow and cause the evaporator coil to get too cold, which can lead to a frozen AC unit. As a general rule of thumb, many HVAC professionals recommend replacing the air filter every 90 days.
The Lifespan of a Thermostat
On average, most thermostats last about 10 years, depending on the model, usage, and proper maintenance. However, many people decide to replace their unit sooner to take advantage of new energy-saving technologies.
It could be displaying an inaccurate temperature. In this case, your car may not be overheating, but your temperature gauge won't be able to warn you. Thermostats can often go bad after about 10 years of use.