That's the sound of the fan motor and capacitor, which work together to circulate air and dispel heat. When they fail, it not only cuts off your supply of cool air. It can also cause your compressor to overheat and the evaporator coils to freeze. But a motor and capacitor don't have to fail entirely to cause problems.
A capacitor is not why it's freezing up. Two things cause an evaporator to freeze... low air flow or a low charge. That is true for 95% of the cases.
Frozen compressors, icy coils, and frosty refrigerant lines are all a product of evaporator coils that are too cold. Nearby moisture in warm air condenses on the cooling coils and freezes. That can make the compressor run hot and burn out. The compressor could also freeze up.
If the start capacitor malfunctions or wears out, it usually prevents the HVAC unit or the blower from turning on. A bad run capacitor won't prevent the unit from starting, but it can lead to the unit shutting down prematurely, overheating or making more noise than usual.
For AC capacitor replacement, anticipate spending between $150 and $400, depending on the capacitor's type and accessibility. A bad AC capacitor is a fairly minor repair, and most HVAC technicians will recommend a repair rather than replacing the unit when the capacitor is the problem.
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.
If your AC capacitor is bad, you may notice that your air conditioner takes a long time to turn on or doesn't turn on at all. In some cases, the damage to the air conditioner's capacitor may be severe enough to prevent the compressor from starting at all.
If the capacitor fails open circuit you probably won't be able to get the motor running, though sometimes they will go (probably at lower speed/power) if you can spin the shaft. And amusingly, they may fail to a wrong value and allow the motor to run backwards.
Test the Capacitor
Place the multimeter probes on the capacitor terminals. The multimeter will display a reading. Compare this reading to the rated capacitance value printed on the capacitor. If the reading is significantly lower than the rated value, the capacitor is faulty and needs to be replaced.
Dirty coil
This prevents it from getting the airflow it needs to properly move heat, which means that the system could then freeze over. Evaporator coil cleaning is an essential part of our AC tune-up service for this exact reason.
On average, AC capacitors last 10 years, but their life span can range anywhere from five years to 20.
It's a small, red button usually located on or around the unit. The button should have a clear 'reset' label. Once you find the button, press it for around three seconds and observe the AC. Check whether the AC kicks on immediately and if it doesn't, press the button again for another three seconds.
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).
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.
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.
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.
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.
If the capacitor has fully gone bad, the AC unit's motor will receive no power and your AC won't turn on at all.
Since AC capacitors are high-voltage components that might cause significant injury to you even if the power is out, it is strongly recommended against changing them yourself. Follow any instructions provided with your new unit purchase if you're thinking about replacing your own AC capacitor filter.
Your capacitor is rated with microfarads. By using a voltmeter, an HVAC technician can determine how many microfarads your capacitor has. A value under 25 is a sign that your capacitor is bad and must be replaced. Although you might own a voltmeter, you shouldn't measure the capacitor yourself.