How to Fix an Ice-Frozen Heat Pump / Air Conditioner

January 15, 2009 | by Kim (email) |

About a week ago, we awoke to a horrible grinding sound coming from our outside compressor unit for our heating system.  We immediately turned our electric heat pump system to emergency heat (which powers down the outside compressor) and then went outside to discover this:

Our compressor was completely frozen over.  We’d had a rainstorm overnight, and while the temperature outside was just above freezing, the fan chilled the air just enough that the rain froze to the unit and then built up overnight.  The sound we heard was the fan blades chipping against the accumulated ice chunks on the inside of the unit.

I called Mike, our HVAC mechanic, and he recommended removing all the ice, then turning the unit back on for a minute to check for the noise.  If the fan ran smoothly, all was well.  If it continued to make the rattling sound, that meant that the blades had been bent by the ice, and we would have a somewhat costly repair on our hands.  So I headed out into the rain with my hairdryer and a scraper and de-iced the unit.

I turned the system back on, prepared to cut it back off immediately if necessary.  Fortunately for us, clearing the ice did the trick, and we had no further damage.

To be safe, I left the heat on the emergency setting until the rain stopped mid-day, so it would not freeze back over while we were out.  And in the future we will pay more attention to freezing-rain forecasts.  Running emergency heat over night may be an expensive proposition – but NOT as expensive as a compressor-parts replacement!

Getting Help with Your Heat Pump or Air Conditioner

If you’d like to get help with your heat pump or HVAC technician from a professional, we partner with ServiceMagic to help people find contractors in their area who can help. There’s a few short questions to diagnose your problem and then they match you up. Here’s the link (the service is 100% free for the consumer):

What do you think? Have you run across similar problems with this extra-cold winter?

41 Responses
  1. Daniel Meyer says:

    I would call your HVAC guy back and ask him to figure out why the unit did not de-ice itself…they are supposed to “figure out” that there is icing conditions and cycle in such a way as to defrost themselves.

    I’ve had heat pumps for years and although I’ve seen the beginnings of ice on mine on occasion, it always defrosted itself before the ice became a performance problem.

    My opinion is that yours is not working right or it would not have reached that state.

    Good luck!

    Daniel Meyer

  2. Jon McDougal says:

    Turn the lemon into lemonaide, I says. Now you have a valid reason to purchase a nice heat gun!


  3. K. Cleaver says:

    I would call him out to find out why it didn’t go into a de-ice mode. That is suppose to keep the ice from building up. Our heat pump stopped de-icing a few years ago and they came out and replaced a circuit board, then all was well again.

  4. Amalie says:

    Glad you posted this– we had the very same thing happen a few weeks ago. Our unit sits right where water runs off the roof and icicles were building up above the blades; I’m not sure the unit would recognize icy conditions since our coils were fine It was just icicles on the grate that protects the blade. Anyway, we did basically what you did and then hung a tarp from the roof to temporarily protect the unit from large quantities of water. I think in the spring we’ll build an extension of the roof that just barely covers the unit, but is high enough to allow sufficient airflow.

  5. Carol says:

    We installed a new heat pump/ac and gas furnace this past summer.
    Our p/h guy said to switch to the furnace when outside temps got down to 20 degrees. Since we’ve been staying below 0 for quite a while now, the heat pump hasn’t been used.
    I do see snow on the unit and wonder if it will damage it.

  6. Leslie says:

    I have never had this particular problem, but I will tell you about a related problem that took forever for us to figure out: The pipe that drained condensation from the propane gas burner in our previous house would freeze up and eventually clog, causing our system to just stop working! Anyone who has a furnace that drains off condensation in that way needs to keep a close eye on it during super-cold weather.

    Wrapping the drain line with insulating tape where it ran through unconditioned spaces helped, and if it was going to be super-cold for an extended amount of time we’d set up a simple work light to keep it warm enough to not freeze. But don’t do anything stupid like I did: Electric pipe tape is NOT compatible with plastic pipes!!! One of my more embarrassing Stupid Homeowner Tricks….

  7. Fred says:

    Hi all – Kim’s a little busy printing out more of our adoption paperwork, so I thought I’d throw in our comments….

    @Dan – definitely true that in most normal situations the compressor will run in a defrost mode that will fix the problem. In this particular instance, we had gotten about 3 inches of rain in 32-33 deg. temperatures. The result was a flash-freezing effect as the rain trickled from our deck down onto the HVAC. I had some concerns about the defrost cycle not running properly but the HVAC guy said that in “the perfect storm” of weather, where rain hits the unit and freezes right away, this kind of icing can occur. I actually sat outside for about 30 minutes a few days later and listened – the unit is properly cycling to defrost mode periodically, so that satisfied me. If we experience the problem and further (e.g., when snows hit later this year), we’ll definitely have someone in to take a look.

    @Carol – your HVAC guy is right. When the temperature gets too cold, the heat pump can actually pump colder air into your house, which will make your furance turn on in auxillary mode. Plus, additional air circulating in the house creates more heat loss. So, when its below 20 (or maybe 15 if you have a great unit), you should run indoor-only.

    @Leslie – too funny about the heating wire – I can imagine that wouldn’t work. But we all make stupid homeowner mistakes … who cares – that’s what makes ownership so exciting 🙂

  8. Parker Darden says:

    Freezing rain has always been a problem. Super cold air is coming out of the unit which is normal. Typically the air will be at least 20 degrees colder than outside air temperature. So you can see if it is near freezing and you get rain freezing on unit is going to occur. A simple way for the homeowner to rid the unit of ice is to shut the unit down and run water over the unit. Ice on grill and fan will melt quickly and you can resume normal operation. This makes short work of it. If freezing rain persists, and you don’t want to do this you can run system in emergency heat until freezing rain stops. Sometimes fan blades will ice up and cause out of balance, vibrations and noise will occur, the fan blades can break. Shut down and simply pour warm water over blades and return unit to service.

  9. Carol says:

    I have been having a problem with my new heat pump all this winter and have lived at two previous houses in the same town that were heated with a heat pump and have never encountered the icing up that I have this year. My electric bill has tripled with this problem.

  10. Colin says:

    I just stumbled across this site while researching heat pumps. I have a heat pump in my cottage in Eastern Ontario. The installer put the fear of God into me about freezing rain and how it could stick to the fan blades causing them to go out of balance which in turn could ruin the unit. I switch to emergency heat when I am going to be away but that kind of deafeats the purpose of a heat pump. A friend of mine just had a heat pump installed and the installed looked at him sideways when he asked him about potential problems with freezing rain. Who is right?

  11. Kim says:

    Colin – having asked around a bit more, we’re pretty sure that this CAN happen when there’s a “perfect storm” (pardon the pun) of conditions – the air temp, the volume of rain (or if the unit is below an area where the water pools), the prior existing conditions.

    We have had no problems with our unit since that day, and there WAS a tremendous amount of freezing rain falling, plus our unit sits under our deck, and the water was running directly onto it from the crack in the deck floor above. This winter has been an average of 10 degrees cooler than normal in our area, so that’s probably why we hadn’t run into the issue before.

    Also, our HVAC guy is a friend, and he advised me over the phone – meaning he got paid nothing. It was certainly not to his advantage to make that up – for the friendship or for business. So we’re confident that the freezing rain was the problem.

    If we find out otherwise, we will of course post an update, but so far what we’re finding is that this does happen – rarely. If it happens repeatedly, then there probably IS a problem with the de-icer, as a few people have mentioned above.

  12. Dwight says:

    Just noticed this issue after not feeling any cool air in the house during heavy rain. Went outside and to my surprise the compressor? inside the outside unit under the fan was frozen over. The copper pipe coming from the compressor was also iced over and the ice was thick. I followed the white iced over pipe until it ended and went into the wall. I turned the unit off for the night and checked it again the next morning. All the ice was gone. The unit is currently working but what can i do to avoid this again? Was it the drizzling rain exponentially freezing as soon as it hit the pipe that caused this issue or am I running out of freon. I guess I’ll run it for 1 hour or so while it’s ccurrently not raining to see if the pipes start to freeze over again.

  13. shannon says:

    I ran into this problem today. I am so glad that I found this site. My heat pump was identical to the pic above. Thanks for the helpul info!!!

  14. Frank says:

    What about putting a awning about 8 feet over the unit to keep most of the freezing rain out?

  15. Samy Mossad says:

    Thanks for this timely information. We’re in Florida and it’s been uncustomarily freezing. Our unit is outside and has a big fence around it because of the HOA requirements to keep the area ‘good looking’. Our unit is frozen on the outside and a light coating on the inside. We’ve been lowering the temp in the house during the day and only using it at night. Everyone’s comments have been extremely helpful. Is there anything you can do if you don’t get full sun and can’t put in the de-ice wiring? My circuit board dies every 2 years (I was told they are very senstive) and the pipes are very close to the house so there isn’t alot to insulate.

  16. Ronald Blevins says:

    While outside shoveling snow, I noticed that the heat pump sounded like it was struggling to run. I looked inside and saw a big chunk of ice the size of a soccer ball forzen on the compressor unit underneath the blades. The blades are not touching the ice. We recently put a metal roof on our house and we have had some huge snows in Virgina the past couple of months and the snow and ice is coming off the house down on the unit. How to you reccommend I correct this problem and would it be ok, for now, to pour hot water over the compressor to melt the ice that is there now. The heat pump was installed in 1996

  17. Kim says:


    It’s pretty cold out, so hot water could potentially freeze on an ice ball that size before it manages to melt it. Definitely turn the outside unit off, switch to your emergency heat for now (if you need it) inside, and see if you can get the ice to melt (a hair dryer would be better than hot water … can you borrow one?).

  18. Colin says:

    Ronald, Kim,

    I do get the occasional ice build up on my blades when we have freezing rain here in Ottawa. You folks refer to it as sleet I believe. At any rate I have poured warm, not hot, water on the fan blades until the the ice melts and is completely gone. Sometimes one bucket does it but never more than three. The point is, it only has to be warm enough to melt the ice. It doesn’t have to come straight out of a boiling kettle. Water that is warm enough to comfortably leave your hand in is fine. Repeat until all the ice is gone. Since it’s water it will run away w/o freezing before you reach your objective. And yes, turn off your compressor and use only the emergency heating unit of your system. It may cost a couple of dollars more to run it that way but it will still be cheaper than having to replace your fan motor and blades.

    Also, you might want to think about ice guards on your new metal roof to prevent the snow from sliding off onto your unit.


  19. harold bowman says:

    Outside air conditioner unit gets very hot very often. Is something wrong? The thermostat is set on 75 degrees and the outside temperture is between 50-85 degrees.

  20. Kim says:

    @Harold Bowman – if it’s really hot to the touch, yes, something is probably wrong. Ours gets warmer than the outside air temp in this spring season, but never truly “hot.”

  21. Tinkerer Putterer says:

    Our Lennox heat pump outside unit here in Maryland, during freezing rain at 2 or 3 in the morning, will grow icicles from the fan guard down to where the fan blades will strike them and sound like a lawnmower. Or the wide fan paddles will collect puddles of water that will freeze in them and when the fan starts not all of the ice leaves and the unbalanced fan causes the unit to shake violently. The noise awakens me and I have to dress for a cold, wet, manual deicing by flashlight. What a GREAT design! We’ve been to the moon 40 years ago but we can’t design an outside unit that can operate outside! I’d rather not switch my thermostat to “Emergency Heat” every time I go away on a trip (or even just going to work) this winter. I called Lennox yesterday and described this situation asking if there was an optional “top” that could be purchased for this unit, perhaps an air deflecting cone facing the fan, the flat top mounted on 1 or 1.5 foot legs, or something. Their technical guy told me there is no optional top and how they rigorously tested these units in snow and ice blah blah blah, yeah yeah yeah, my problem doesn’t exist – Oyster feathers! He also said my unit needs 48 inches of clearance, it was installed under my open stairs to my deck. I have the home videos of the fan hitting the icicles and the violent shaking from the ice puddle in a fan blade and will put them on YouTube. My neighbor has a unit made by Trane which has the problem-free design (solid top, vents on the side above the coils). Thank you for this Web site, I know I am not alone with my problem. I think I will put a piece of plywood on the underside of my deck stairs just above the unit, enough air will escape unhindered and hopefully freezing rain will stay off of the grill and fan blades.

  22. Kim says:

    Haha! “We’ve been to the Moon…” – yes, indeed. Thanks for the laugh. And yes, a piece of plywood under the deck (or a strategically-place out-door rug ON the deck) should do the trick. Great tip, Tinkerer Putterer!

  23. Houston J says:

    Thanks for the advise but……… If you turn your AC unit to COOL it will melt the ICE who would have thought….. I just opened my electric bill expecting to see a little higher bill due to the cold weather here in the Northwest to find it had doubled!!! Still half the cost of anywhere else I have lived but double WOW!! I immediately walked outside to take a look at the AC unit and wow it looked like a huge ice ball covered 3 inches thick. I was about to hook a hose to the hot water heater to try and remove the ice to allow the unit to work then I remembered what the refrigeration engineer said about cooling a freezer ” I work in a 300,000sf freezer” he said when you drop the temp in a freezer you are not pushing in cold air you are removing the hot air and it goes out the condensers…. I thought it would work the same way at home and defrost my condenser so I turned on the AC and POOF!! the ice began to melt YAY!! Hope this resolves my double electric bill…. We will see next month.

  24. Steve Mattingly says:

    Suggestion For ice roof it or tarp it

  25. Steve Mattingly says:

    Heat pumps are only designed for about 10% of the aera in the us. Georgia and north is a bit more of a risk for ice but if you do get one have a plan B ready and ice is not a every year event in most areas at this tine

  26. Jill says:

    I also have the problem of my heat pump filling up with ice in the winter forcing me to use the emergency mode and causing an enormous electric bill. I have had the circuit board replaced several times, the unit serviced, etc. My HVAC guy is very good, but each year the problem gets worse. I do think it has everything to do with the heat pump being the wrong type of unit in colder climates. I am in Indiana. My HVAC guy says that the main problem I am having is that when the unit defrosts, the runoff freezes in the bottom and plugs up the drain holes – this does appear to be accurate as that is exactly what appears to be happening. It builds up until there is a tremendous amount of ice in the bottom of the unit. Has anyone ever tried heat tracing their unit to allow the ice to melt and run clear? I have been thinking about trying this, but wanted to know if anyone has any experience with trying it.


  27. Colin says:


    I am hardly an expert but does your unit have a sensor that won’t let the compressor run if it it is colder than a preset temperature outdoors? Mine is programmable and set to stop the compressor if the temperature drops below 10 degrees F. Prior to having that sensor installed, my compressor would run no matter how cold it was outside. That can’t be good. It now switches to emergency electric when it is too cold for the compressor to run efficiently. Just a thought.


  28. Jill says:


    I am pretty sure mine does not have the sensor you describe. It does not automatically switch to emergency, I have to do that manally, and the problem is I don’t always think about it until there is a huge amount of ice in the bottom. I agree with you that it can’t be good for the compressor to run continually, and that is what mine does until I realize it is filled with ice and switch to emergency. I will have to ask my HVAC guy about that sensor. Thanks for the tip!


  29. Colin says:


    I copied the compressor make and model number information and contacted the manufacturer directly then I passed along the part information to my HVAC guy. It involved installing the sensor and a new thermostat to accommodate the sensor signal.It cost about $500 for parts and labor but I sleep a lot better, especially when I am away for extended periods of time.

  30. Kim says:

    @ Colin – Thanks for jumping in there and helping Jill out!

  31. Jill says:

    Thanks Colin.

    It was 40 degrees here yesterday and still the unit is filled with ice. I poured 3 buckets of warm water over it in an attempt to melt the ice, and still there is about 6 inches of solid ice in the bottom of the unit (there was a foot before). I have had it on emergency for a week now, the temps have been over 30 during the day, and still it is iced up pretty bad. I am wondering if the freon (or whatever is in there these days) needs to be charged, or if maybe the evergreens I planted just south of the unit which have grown tall enough to block most of the sun it used to get, may be the culprit. None of my neighbors units are iced up, and none of them have planted bushes to the south of the unit as I have. Didn’t think aobut the need for it to have sun in the winter – but I bet those bushes are helping in the summer! Been spending time looking at it to try to figure out why it has gotten worse over the years (it is 10 years old). Maybe there are environmental factors like the evergreens, etc.

    I’ll have to call my HVAC guy and talk with him about your suggestion and my observatoins. Maybe we can solve this yet!

    Thanks for all your advice.

  32. G Taylor says:

    I went out for a few minutes this evening and when I returned, my daughter screamed she heard a loud noise just outside under our bed room window, prior to that when leaving my car I was hearing a metal scrapping like noise, which I thought was coming from the adjacent homes unit. We to make a long story somewhat short, befor leaving home I was noticing my lights flickering (faintly) once in a while like something was turning on or off. Well something told me to investigate outside, and to my surprise, my unite was frozed with ice on the blade and covering the top and side vents. The Blade was also stuck. after reading some of the advice posted I tried them all but the hot water and hair dryer, ( I did not want to get shocked!) I just turned the unit on a/c and lowered the temp to 50 degrees and watched the ice melt, once it finnished I turned everything on back to normal and all worked well. This was very helpful, and I will follow through with a maintenance check tomorrow. Thanks all for your great! advice. Sorry for being so long winded, I thought everylittle bit counts.

  33. HANDYMAN51 says:

    Thanks to all above for this input. It will give me rational steps to take before I head into my normal ” sky is falling” mode!

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    • Freddie says:

      I have a hail 7000 hear pump that freezes up on the out side of it you can’t keep it on to long can you tell me what it can be makeing it do that

  36. George SNOW says:

    My outside compressor has ice on the pipes and the A/c is NOT working… Also, can the fan control switch will only work in the AUTO position and will not run when switched to the ON position.

  37. ABDUL KHALID says:


    My outside compressor has ice on the pipes and the A/c is NOT working… Also, can the fan control switch will only work in the AUTO position and will not run when switched to the ON position.

    This is copy and paste of George SNOW.
    is any one have any idea, can you please reply on my Email.
    need to save money before call tech.

  38. Bobbie Barker says:

    So We’re in Austin TX we never get that much ice but today was bad.. the Trane compressor was humming but no fan covered in ice. I used hot water and a gentle knock using a stick to free ice from the top and sides and got the fan to finally come on. it’s a heat pump by the way so that’s part of the problem. Is that the best way. We are going to seriously look at some way of putting a roof over the top of the compressor.. nothing low enough to block the fan but to keep further rain (ice) from accumulating.

  39. Sarah says:

    Same here this morning in TN, Bobbie. About 16 buckets of warm water later and everything is unfrozen. Thank you for this blog post, still relevant 12 years later!

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