If your blower motor is not functioning properly, it can't circulate air through your AC system, causing the evaporator coil to become too cold and eventually freeze up.
If the system gets low in refrigerant, low enough, it will freeze the evaporator coil up, and that will lead to reduced air flow. The inverse is also true a blower that is not moving enough air or ductwork that is undersized or restricted in some manner can also cause a freeze up.
A blower motor is the part of an AC or furnace that controls the amount of air pushed through the air handler. A motor's performance can largely affect air conditioners' functionality in meeting industry standards. Blower motors typically come in two types – single-speed blower motors and multi-speed blower motors.
An Overheating HVAC System
If your blower motor starts to go out, it can cause the rest of the system to overwork and heat up.
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.
The most likely reason your air conditioner coils are icing up is a lack of airflow due to a faulty fan motor capacitor. This part aids the fan in circulating cooled air throughout the room.
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.
A Failed Motor
An HVAC blower motor will occasionally fail due to age, wearing out, or not being cleaned regularly. Symptoms may include strange noises, burning smells, or just plain refusing to turn on. If this happens and the motor is no longer operable, a new blower motor may be needed.
Blower motors are designed to last just as long as your furnace itself, anywhere from 10 to 20 years. Just as with any HVAC system, the better maintained and serviced your equipment is by experienced HVAC technicians the longer it will last and the fewer repairs you'll face.
It's possible that the problem will go away on its own, but you'd be leaving yourself open to a lot more potential damage if you sit back and hope for the best. It's better to take care of a frozen unit right away in case there is a larger problem hiding under all that ice.
If the indoor blower fan has malfunctioned, cold temperatures outside the home, or low refrigerant charge, the evaporator coil can freeze. If this happens, call your local Trane expert for professional assistance.
You will hear the capacitor clicking every few seconds if it is bad. This noise is the capacitor trying to release the energy needed for the unit's motors to start. If the start capacitor fails, you will typically hear the motor make a loud humming noise.
This is usually caused by low refrigerant levels, insufficient airflow over the coils, defective fans or components and dirty filters which restrict air flow. It's important to make sure your AC is always well maintained and checked regularly to avoid an unwanted freeze!
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).
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.
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.
If the motor is making rattling, clanking, or banging sounds, it may be because of a loose or broken part inside the system. Loud banging sounds are especially worrisome. They're usually a sign that something within the system is damaged or disconnected, potentially indicating the need to replace the blower motor.
On some platforms, a faulty blower motor relay will cause the blower not to work at all, which means there will be no airflow from the A/C. On others, the blower won't work on “high blow” but all the other speeds will work. The blower motor relay fails because it regularly deals with high current loads.