Help, I have a frozen AC system!

It is a hot summer’s day and your AC suddenly stops working. You walk outside and see ice all over your air-conditioner… you have a frozen AC system.

All you need to do is turn it off and let it melt, that will fix it! Wrong.

The real problem starts inside on your indoor coil. This coil will be completely encrusted in ice and it can take hours to melt. Until it has thawed you can’t get any air through the cooling coil, turning it off for a while and turning it back on without looking into the cause of the freezing, will result in another freeze up.

Generally, a frozen AC system will have to thaw overnight for 5-8 hours due to the thickness of the ice. You have to be very careful during this thawing process because that ice will melt and cascade down on the furnace, many times burning out components in the furnace.

Often homeowners think the problem is fixed with the AC starts working again, and cancel the service call before the technician arrives. Yay, it’s magically fixed… then it stops working again and they call for service again, delaying the repair and extending the discomfort.

If you ever see ice you have to call for help there are a couple of reasons why an air conditioner can freeze up:

  • Dirty air filter – if you don't have enough air flowing across this coil it will start to ice
  • Low on refrigerant – when the freon drops in a unit the surface coil temperature drops so cold that the water that's being removed from the air freezes. The surface gets blocked with ice then that ice starts building up and building up. It works very much like the ice maker in your refrigerator so icing is always a potential problem
  • Restricted airflow  – you have furniture or other debris blocking a floor vent
  • Setting the temperature too cold
  • The AC system is too big for the home

If you don't have a dirty filter and you don’t see another obvious source of restricted airflow, then you need to:

  1. Call your air conditioning contractor – this problem doesn't fix itself (unless it is just a dirty air filter).
  2. Turn the AC system off – let it thaw out before your service technician shows up
  3. Don’t turn it back on until we arrive and assess the situation

One of the biggest issues that we have with frozen units is people call for help and they think if they leave the air conditioner running they're going to have a bit of cooling while they're waiting. This is not true. No air is getting through when everything is frozen. You can actually burn up your air conditioner if you leave it running while it is iced up. And most importantly, the system will still be frozen with ice when we arrive making it impossible to work with. We will have to leave and make another appointment. This makes the homeowner unhappy of course and us too, we want to help you, but we can’t until it is thawed.

Airflow is everything. A healthy system relies on adequate air flow.

For more helpful home HVAC tips, stop by our blog regularly. In addition, for help with your home comfort or plumbing systems, call the HVAC specialists Woodbridge locals always recommend at (703) 670-8519.


Check out our other blogs for some great HVAC advice: