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Is your air conditioner frozen?

by admin on April 9, 2012

See the white stuff in the top portion of the unit? That's ice, and it's not supposed to be there.

A/C Frozen Up?

The most common problem during the cooling season is the frozen a/c.  You’ve probably seen it yourself.  The copper pipe at the outdoor unit has a thick coat of ice surrounding it.  You may have even found the indoor unit soaking wet because the evaporator coil has turned into a solid chunk of ice.

What causes an a/c to freeze up?

The most common cause is a system that is low on refrigerant, or Freon, but that’s not the only cause.  A system that is not moving enough air through the duct system can also freeze up.  Low airflow could be caused by an under-sized duct system, a dirty filter, or even a dirty indoor evaporator coil (often called an A-Coil).  A frozen system can also be caused by setting the thermostat too low at night.  What’s too low?  Every house is different, but we’ve seen units freeze up at night when they are set to 68 degrees.

What should you do if you’re a/c freezes?

#1  Turn the a/c off at the thermostat.

#2  Check your filter.  Is it wet?  This means the evaporator coil is frozen up, and the water that is melting off it is missing the drain pan.  You better get some towels to line the floor to keep the water from ruining floors or ceiling when the chunk of ice really starts to thaw.

#3  Is the filter filthy?  If not, you’ve probably got an issue that is going to require a trained professional.  I’ve heard Atchley Air is pretty good, so you might want to call them.  If the filter is filthy, throw it away and proceed to Step #4.

#4  Switch the Fan to the “On” position at the thermostat (leave the a/c turned to “Off”).  This will help move more air across the frozen coil so it will thaw faster.

#5  Now you can head to the hardware store to get another filter.  Don’t spend more than $10 on this one.  Until your system is thawed out, it needs as much air as possible so don’t buy the $25 allergy filter that is probably too restrictive anyway.

#6  When you get back home, visually inspect the outdoor copper lines and the indoor coil for ice.  It can take a couple of hours for all that ice to thaw, so you may need to give it a little more time.

#7  Put the new filter in, and turn the a/c back on.

#8  Keep a close eye on the system.  If ice reappears, turn the a/c off and call a professional.  If the system doesn’t start to cool the house down within a few hours, turn the a/c off and call a professional.

Could it be something else?

Other reasons for a frozen a/c could include a dirty indoor coil (that limits air flow), too low a temperature setting at your thermostat (remember, it’s an air conditioner, not a refrigerator), or an undersized duct system.  Most of these items will only be diagnosed after the dirty filter or low Freon charge are ruled out.  To be safe, Atchley Air recommends that you call a professional for an accurate diagnosis.