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Problem: Air conditioner is freezing up. Seeing frost or ice on the suction line (black insulated line)

Happy AC

Problem: My air conditioner is freezing up. I am seeing frost and ice on the suction line (black insulated line) Any areas that are not insulated are covered with ice. My air conditioner is freezing up. You see frost or ice on the suction line (black insulated line) Any areas that are not insulated are covered with ice. You are not getting hardly any air flow out of your registers. Your evaporator coil is iced up completely.

Solution: Turn your air conditioner off and let the ice thaw out by running the fan (fan set to ON) on your thermostat. Thawing sometimes takes 2 to 3 hours.  Most of the time air conditioner freeze ups are caused by the system being low on refrigerant charge. Look for these causes for why the air conditioner is freezing up. Some thing that cause air conditioners to freeze up are:

1. Dirty air filter or some air flow restriction.
2. Dirty blower
3. Slow or dragging blower motor (might need a new capacitor). Please click here if you would like to see the capacitors we sell.
4. Dirty stopped up Evaporator coil (Need to have HVAC tech or you need to inspect and possibly clean evaporator coil)
5. Long Air conditioning run times. Setting thermostat below 72 degrees with cool outside conditions.
6. A stuck contactor that keeps the outdoor unit running even when the indoor blower is not running or when the thermostat is calling for cooling. Please click here if you would liked to see the air conditioner and heat pump contactors that we sell. Please click on this link if you are interested in viewing a YouTube video on how to change a contactor out: YouTube Video on how to change out a contactor.

7. Duct work that is too small or restricted. Make sure that the supply registers and returns are not restricted. In other words make sure all supply registers and dampers are open. Make sure all return grills and registers are not restricted with furniture or obstructions.

Most of the time a freeze up condition is caused by a low refrigerant charge. Since the air conditioning system is supposed to be a leak free, a sealed system this means you have a leak somewhere. I use the Schrader valve caps to make sure that I do not have a leak in the Schrader valves when I take the manifold gauges off. I install these Schrader caps for insurance, because I have seen leaks in these valves many times. These caps have a rubber seal inside of them and insure a leak proof seal. Please click here if you would like to see the Schrader valve caps that we sell. Please click here if you would like to see the EZ Seal leak sealer we sell.  This sealer will circulate throughout your air conditioner or heat pump system and seal small leaks. Below we have a YouTube video that a company called HVAC Maintenance made that shows how to find leaks and install the EZ Seal Sealer. I hope this will help you solve your air conditioner leak problem.

Above, Schrader Caps Installed on an outdoor AC unit.

Below we have a YouTube video below made by David Jones that shows how to install the EZ Seal Sealer. I hope this will help you solve your air conditioner leak problem. We sell the EZ Seal Kit and Sealer on the following page: Please click here if you would like to see the EZ Seal leak sealer we sell.  Thanks so much HVAC Maintenance for taking the time to make this informative video!

32 thoughts on “Problem: Air conditioner is freezing up. Seeing frost or ice on the suction line (black insulated line)

  1. I have a 2 ton R410a heatpump system that was freezing up from the TXV all the way through the suction line in cooling mode. The suction line is only showing about 60PSI and the liquid line about 340PSI. I tried adding just a little bit of charge just to see what response I got, but adding charge to the suction line only really seems to make the liquid pressure rise. The TXV will start frosting within 5min of turning it on. I tried putting the TXV bulb in warm water. That may have raised the suction pressure 5PSI and it appears that kept the top half of the TXV from turning to frost (probably because of conducting the warm waters heat via the bulb) but really no other difference. I’m thinking maybe there’s something wrong with the TXV? I haven’t got around to checking subcooling, but figured that shouldn’t even matter till things are at least close to right? Fans are all working great/ just changed the filter. I’ve done several minisplit single hook up systems but never one of these so looking for a thought. Thanks

    1. Hi Jayson! Yes, it sounds like you might need a new TXV valve. Sounds like the TXV is not allowing enough refrigerant into your evaporator coil. The HVAC industry has had lots of recalls on faulty TXV valves in the past couple of years. Here is a link to a good YouTube video where a service tech at T&N Services tells why so many TXV valves are going bad. He starts talking about the TXV problems about the 6:30 time mark in the video. https://www.youtube.com/watch?reload=9&v=Amo2eRlYrzg I hope this helps you out. Steve

  2. I recently installed an arcoaire 2 ton condenser with evap coil using txv metering device. Bulb is placed inside the evap coil cabinet. I am getting low suction pressure and ice build up on suction line. Pressures read between 110-65 degrees F (starts higher but drops as line freezes up). Charge is sufficient if not over charged due to the issue. What could be causing this? I am leaning toward something with the txv or sensing bulb? Is it bad? Or should i move the sensing bulb outside the evap cabinet?

    1. Hi Michael! Yes, this sounds like you have a TXV problem. Yes, you can set the bulb outside the evaporator and see if the condition improves. It sounds like the TXV is not allowing enough refrigerant through your evaporator. I would suggest checking the charge using the subcooling method. Also, make sure that you have good airflow from your blower. A slow blower motor or restricted airflow as you probably know will cause freeze-ups. We have a really good post about charging air conditioners and heat pumps on the following page: https://arnoldservice.com/how-do-i-use-and-read-a-refrigerant-gauge-set-how-do-i-check-my-ac-or-heat-pump-refrigerant-charge/ You might need a new TXV valve. I hope this helps you solve the problem.

  3. My unit is frosting up at suction line the one with the black insulation the compressor fan comes on but cold air blows out then cuts out any help would be a appreciate thanks

    1. Hi David! This sounds like your blower motor on your furnace or air handler is cutting off while the outdoor unit is still running. You might have a weak blower motor capacitor, a motor that is going out (need a new blower motor) or a fan relay on your control board might be going out (might need a new control board). If the blower motor is going off during a cooling cycle then I would recommend that you check your blower motor capacitor to make sure that it is in good condition. We have a really good post with two YouTube videos that explain blower motor troubleshooting on the following page: https://arnoldservice.com/problem-fan-will-not-come-position-fan-will-not-come-turn-thermostat/ I hope this helps you find and fix the problem soon.
      Steve

  4. Hi,
    I have installed two air conditioner 2 , 2 tons in induction hardening machine , one air conditioner auto on /off from digital temperature meter , another air conditioner running continusally , in this air conditioner ice coming on evaporator , suction line& compressor also coverd with ice
    Kindly reply me what can I do for rectify this problem

    1. Hi Abdul! All that I know that could be your problem is covered in the post above. If your air conditioner is charged up properly and you have good airflow then you should not be having a freeze-up condition. I am sorry that I can not be of any help other than the post that I wrote above. Steve

  5. Please, I replaced the compressor for one of my split unit. But after gauging n ensure it was properly gauged I noticed the suction was freezing.. Pls what could have caused it. Thanks

    1. Hi! There are many things that could cause your unit’s suction line to start freezing. We have a post that covers some of the reasons on the following page: https://arnoldservice.com/problem-air-conditioner-is-freezing-up-seeing-frost-or-ice-on-the-suction-line-black-insulated-line-any-areas-that-are-not-insulated-are-covered-with-ice-hardly-any-air-flow-out-of-your-registers/ A TXV Thermostatic Expansion Valve that is not working properly or a restricted metering device could also cause freeze-ups. I hope you can easily find and fix the problem. Steve

      1. My air condition indoor coil, out door coil clean. But that Ac good worke 8 days or 10 days.after suction line freez.after turn off to unit 5 hours. After again work 8 or 10 days perfectly. And after suction pipe freez.whats the problem this Ac please give to any solution?

      2. Hi Rishman! Problems that cause air conditioners and heat pumps to freeze up are covered in the post that I wrote above. Most of the time air conditioner freeze-ups are caused by having a low refrigerant charge. I would recommend that you have your air conditioner checked to make sure that the charge is correct. Also, make sure you do not have any of the problems that I wrote in the post above that cause freeze-ups. I hope you can find and fix the problem soon! Steve

      3. I installed a 5 ton r410 AC, 5ton Coil Upflow and New ECM 135K Btu gas furnace and corrected return air issues to get 2000+ cfm and my txv has been changed also filter drier is at the coil. My lineset is 50 plus ft long 7/8 x 3/8 my suction pressures start out at 109 psig but drops to 92 psig, my discharge pressure is 292 psig. The txv and bulb is located inside of the evap cabinet the temp at coil is 27.5°F. Would I be able to clear restriction by pumping down AC and disconnecting liquid line at the txv?

      4. Hi Mr. Benford!
        I hate for you to have to replace the TXV, but if the bulb is not sensing right or if the TXV is restricted then you might need to replace it. I would try to move the sensing bulb to outside on the suction line and see if the pressure-temperature improves. Hopefully you can get more refrigerant through the system and this will fix the problem. If not then all I could recommend would be a new TXV valve. Sorry that I can not be of more help. Steve

  6. Hello. I have carrier 1.5 ton split ac. The thick pipe at the outside unit shows ice on it. The cooling has reduced. The tech says it because of dirt in the coil and low gas. I just wanted to know if the tech was right or there is some other problems. Thanks

    1. Hi Zak! Yes, most of the time when a unit is low on charge it is caused by a leak in the system and the system being low on refrigerant. It can also be an air flow problem like a dirty evaporator coil, dirty filter, dirty blower wheel, slow blower motor (might make sure capacitor on motor is in good condition) or restricted duct work. Yes, I agree with your tech. I hope you get it fixed soon! Steve

  7. Hi Steve, my unit is new, installed in January of this year, and is getting ice on suction line insulation. Thoughts on this being that it’s so new? Many thanks….. Mark

    1. Hi Mark! Sorry to hear that the suction line is freezing up. Maybe you have a slight leak in the system that the installers left when they brazed your lines together. I would like to suggest that you turn the unit off and let the fan blow until the evaporator coil thaws. This could take a couple of hours of blower run time. Other causes for the freeze up would be a restriction in the duct system, dirty filter or a slow or dragging blower motor. You might try to set the blower speed to a higher speed and make sure the capacitor is in good condition. I hope you can get it back running right again. Hopefully, your unit is under warranty. Hope you have a great day and weekend! Steve

  8. Hi Steve, I have a straight a/c packaged unit (2 ton) that runs fine for a few hours cooling nicely. The charge is correct, all capacitors are new, blower runs fine, filter and both coils are clean. It has capillary tubes and a copper spun filter dryer. My problem is that after a few hours the compressor and suction line get severely iced up and the unit starts blowing warm air. It does not appear as if the evaporator itself is iced up though. Super heat will just start randomly plummeting and then climb back up. Do you think there is a restriction in one of the capillaries? What else could it be? Thanks in advance for your time.

    Ken

    1. Hi Ken!
      Testing with gauges and watching the gauges to see what the pressures are doing should tell you what is going on in your system. If the suction pressure starts out right and then starts going down then you probably have a restriction in the system. This could be water that is freezing up causing the restriction or a TXV valve that is not working correctly. I would suggest going to the AC Service Tech channel and looking for YouTubes on restrictions in ac systems. Here is a link to some good YouTube videos: https://www.youtube.com/results?search_query=restriction+in+ac+system I hope you can easily find and fix the problem. Steve

  9. I have a ac unit that the pipes is cover with ice do I need to stop the ac and turn on the fan on the thermostate or let it dry on its own

    1. Turn your air conditioner off and let the ice thaw out by running the fan (fan set to ON) on your thermostat. Thawing sometimes takes 2 to 3 hours. Most of the time air conditioner freeze ups are caused by the system being low on refrigerant charge. Look for these causes for why the air conditioner is freezing up. Some thing that cause air conditioners to freeze up are:

      1. Dirty air filter or some air flow restriction.
      2. Dirty blower
      3. Slow or dragging blower motor (might need a new capacitor). Please click here if you would like to see the capacitors we sell.
      4. Dirty stopped up Evaporator coil (Need to have HVAC tech or you need to inspect and possibly clean evaporator coil)
      5. Long Air conditioning run times. Setting thermostat below 72 degrees with cool outside conditions.
      6. A stuck contactor that keeps the outdoor unit running even when the indoor blower is not running or when the thermostat is calling for cooling. Please click here if you would liked to see the air conditioner and heat pump contactors that we sell. Please click on this link if you are interested in viewing a YouTube video on how to change a contactor out: YouTube Video on how to change out a contactor. I hope this helps you find and fix the problem. Steve

  10. Hi everybody I had a service call package unit 5 ton 410a.
    Get freez up the suction line and the the compressor , I changed the filters and I cleaned the condenser, I cheated the blow is runing good when I measure the low side with my gauges suction. Line 65 psig and lequid line 325 psig I cheated the return is clean when I chard the unit I hear the compressor going bad it mean is overcharging , I don’t know the problems is the filter drayer or the txv

    1. Hi Karem! Sounds like a bad TXV valve. I heard that many of the manufacturers are having trouble with their TXV’s because of the rust inhibitor that Copeland is using in the compressors. The rust inhibitor reacts with the oil and causes a substance to form on the piston pin of the TXV and this substance causes a restriction inside the TXV valve. The follow is a good explanation of why so many TXV valves are going bad: https://www.youtube.com/watch?v=Amo2eRlYrzg Fast forward to 7 minutes if you want the explanation on the cause of the problem. Here is a link to some good videos on troubleshooting TXV valves: https://www.youtube.com/results?search_query=troubleshooting+txv+valves AC Service Tech has some real good videos. Rarely do filter driers get stopped up so I would think the TXV is bad. I hope you can easily find and fix the problem. Steve

  11. Thank you and you have a Blessed day aswell,

  12. I have a heatpump that has ice on the highside botton line on the core which the high pressure switch is. It start at highside charging valve and end at high pressure switch. no where else. auto heat blowing cool. This is heat setting auto.

    1. Hi William! There are many things that can cause a heat pump unit to freeze up in the winter time. Most of the time it will take a technician with gauges to troubleshoot and find what the problem is. Some of the causes for heat pump freezing in the winter are low refrigerant charge, faulty defrost control board, faulty defrost thermostat, stuck reversing valve, restriction in the refrigeration system and a slow or dragging outdoor fan motor. I would suggest that you have a service tech check out your heat pump. Sorry that I can not give you a DIY answer. I hope you have a Happy and Blessed New Year! Steve

      1. My ac lines keep freezing up, wash washed the condenser, Checked that the vent were clear, tested the blower motor, still nothing. When I unplug the wiring harness that contains the blower feed, and give direct power to the blower it works fine, but when I put everything back to normal and use the wiring harness, the fan gets no voltage. So what could be inside that furnace wiring that is stopping the circuit board from sending power to the blower?

      2. Hi Tobias!
        There could be a bad connection in the wiring harness or control board. If you are getting 110 to 125 volts into the control board between L1 and neutral and not the right voltage 110 to 125 volts out to the blower motor then the control board is at fault. Most of the time freeze up are caused by low refrigerant charges, but yes a slow or blower motor that does not work can cause freeze ups too. I hope you can find the problem soon! Steve

  13. I will be happy to try and answer any questions you have. Thanks so much for your interest and support in our website! Hope you have a blessed day! Steve

    1. Hi Steve … I have an OLD HVAC, R22 unit … In past few months on exceptionally hot days, the cooling inside home becomes weak… Do you have any thoughts on #1 could my compressor be short cycling causing this brief period of warm. I changed the capacitor to no avail. The condenser is clear and there are no signs of freezing, ie… low R22. #2 knowing unit was old last winter I anticipate replacing but hoping to get perhaps a year or two more out of this unit. Note that the unit DOES cool my home great as I can set it to 68 and inside of the home will be COLD in mornings. Also, between a home warranty outfit that I would not recommend to anyone and a technician who came out, took a look {NO TESTING whatsoever} and submitted a diagnosis back to warrant co. for Condensor/coil replacement {whick btw warranty co denies, I am about to “Blow My internal thermometer” LoL … Any feedback/insight will be greatly appreciated. Thanks in advance. John

      1. Hi John! Most of the time when a unit does not cool properly on a really hot day it is caused by the system being low on refrigerant charge or the condenser coil is dirty and needs cleaning. I would suggest that you make sure your outdoor condenser coil is clean by turning off the power to the unit and cleaning the coil with a garden hose. It is best to clean by spraying from the inside out so you might have to remove the top to spray inside to out. Also after the water has evaporated off the coil test the refrigerant charge to make sure your unit is charged up properly and the metering device (TXV or piston pin) in your evaporator coil is working properly. If you have a TXV you would use the subcooling method for checking the charge. If you have a piston pin you would use the superheat method for checking the refrigerant charge. The following AC Service Tech channel is a great source of information about solving air conditioning problems. Here is the link to that channel: https://www.youtube.com/channel/UCOZR-1IqsAer9wzlvFgb4mA/videos?reload=9 I hope you can easily find and fix the problem. Steve

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