FAQs about refrigerant piping or suction line ice & frost formation diagnosis & cure: refrigerant line frost cause & remedy.

This air conditioning repair article series discusses evaporator coil icing: the problems of ice and frost formation in air conditioning system air handler units, blower units, or AHU's, duct work, or other air conditioning system components.

A freezing or frosted A/C coil blocks air flow and leads to loss of coo

Frost or Ice May Appear on Refrigerant Line FAQs

These questions & answers about frost or ice formed on refrigerant piping were posted originally at FROST BUILD-UP on AIR CONDITIONER COILS - please also review the diagnostic advice given there.

Frost and ice can even form inside air conditioning duct work, leading to troublesome leaks into the building. This article explains locations and causes of condensate, frost or ice formation in air conditioning systems, air handlers, compressor/condensers, refrigerant lines, and in air ducts.

On 2019-04-30 by (mod) - icing on high pressure line in a truck A/C system

RE-posting from private email:

Anonymous said:

I might not be emailing the right spot but I need help figuring out a problem, it is on my 2007 Dodge Ram truck. The AC in this truck is blowing cool but not as cold as it should be. I borrowed some gauges and got readings on the high side of 125 psi and the low pressure went up as high as 95 after 15-20 minutes. I shut the truck off then. I also noticed the high pressure line icing up from the firewall to about halfway forward upon which it was cool and sweaty there. Can you tell me what my problem might be? I just bought this truck in January so I don't know anything about the history as far as AC work.

Moderator's brief reply:

typically there's either low refrigerant or a bad refrigerant metering device. The high pressure line is usually hot not cold and icy.

On 2019-03-24 by (mod) -

Ahmed it sounds as if you found the problem - a sticking TEX (TXC or thermostatic expansion valve)

On 2018-08-10 by Ahmed

After my york chiller start ice forming on suction line and compressor although i replaced new tex and filter drier and refrigerant pressure is ok

On 2017-07-03 by Doug Gray

I have a 2.5 ton packages unit amana 8 years old,cap tubes frosted up . Evap coil clean, blower running on high speed. I only have a 12 degree TD. Duct system is all flex ductwork . Both coils evap. And condenser look clean. Where might problem be .

On 2017-06-29 by takudzwa hapana

@Puranmal,
tell me what causes difficulty in formation of ice in refrigeration unit.

On 2017-06-29 by takudzwa hapana

tell me what causes difficulty in formation of ice in refrigeration unit.

On 2017-03-26 by Anonymous

My chest freezer works for a while then I notice that the copper pipe freezes

On 2017-02-23 by (mod) -

Pressure is not constant in a refrigeration system - it will drop on the high side and increase on the low side when the compressor motor stops.

On 2017-02-23 by taina

I installed chest freezer compressor into a two door fridge.when i test it,the pressure keeps dropping.why is that?

On 2016-11-13 by (mod) -

Puranmal

Normally the tech pulls a vacuum on the line and then installs filter/driers. If the line is blocked I'd prefer to cut and replace that section.

On 2016-11-13 by Puranmal

Have biggest problem in Refrigration. Some copper tube or cooling in side choked, so how to fulsh tube line

Question: had the AC coil replaced with a used one - would this cause ice up on the compressor/condenser

had a coil changed out, on side of box stated that this coil was filled with new 410 refridgerant. the unit outside was replaced with a used one and the installer said he used r22 , would this caused a coil to ice up and back up to outside unit? - Cathi 6/7/11

Reply:

Cathi: certainly mixing two different refrigerants will not permit proper air conditioner operation.

Question: the hvac tech added refrigerant - what should I do to avoid repeat service calls?

My AC output was low for some time. On opening the cover I noticed heavy icing on cooling ducts. The young technician who came instantly said that gas had leaked and it requires a refill. Should there be other reasons to avoid repeat technician visits? - Kulbir Labana 7/30/11

Reply:

Kulbir: yes, if the refrigerant gas has leaked out of the system then just putting more refrigerant in is only a temporary fix. You will want a service tech to find and fix the gas leak or other causes of icing that are described in the article above. .

Question: frozen pipe outside my air conditioner unit - bad switch not lost freon?

Pipe frozen at outside unit and the inside unit would stop running but the outside unit would continue to run. I made an appointment for service. The tech came out and checked my freon level, he said it was fine and suggested that my problem may be the compressor. I told him that I was out of town all week and did not notice any problem before I left.

He then told me that severe weather came through the area a few days prior and I should call my insurance agent to file a claim. The insurance agent sent someone out to check it. This turned out to be another heating and air company.

This guy said that the freon levels were good but s switch needed to be replaced. He replaced it but three weeks later I have the same problem and have no idea what to look at myself to see what the problem could be.

My air filter is new. Both units come on and off together. No registers are closed. I checked for dirty coils outside then went into the attic, up there the coils had frost on them hours after I shut everything down. - Jason 7/30/11

I have the same problem as Jason, only it is intermittent (once every two weeks or so). Ha,ve had two contactors(?) replaced since last year. What can I tell repairman to test next? - Jackie 8/2/11

Reply:

Jason if your inside unit (air handler, cooling coil, blower fan) stops running, I'm not clear how a bad outdoor compressor would make the inside air handler unit stop. A bad switch can be the culprit and sometimes even a replacement part can be bad, or the conditions that burned up the first switch could burn up the second one, indicating that more careful testing and diagnosis to find a root cause are needed.

Jackie, I would be careful not to be too directive to the repairman; but I would press for an explanation of why the same part keeps being replaced; it's natural to suspect that a different problem is damaging the part that's being swapped out.

Question: if I close off the upstairs will that solve my air conditioner compressor and evaporator coil problems?

I've read through a ton of comments here, and I appreciate all of the answers you gave. It seems that there's only three causes for the evaporator coils icing issue. We moved into our house here in south Texas from Alaska about 9 months ago. It was a foreclosure, but things were in good shape, except for the compressor.

The sellers agent replaced it free of charge and worked great up until 3 months ago. That's when the problems started.

First they could a leak in a joint right on the outside of the in-house unit, he refilled it with 5 out of the 12lbs that are supposed to go into the unit. 2 weeks later, another call to the tech cause of an icing issue. This time, with dye and an electronic sniffer, he said it was the coil itself, and it was COVERED in rust. $1000 later, labor only, thank you carrier warranty, i have a new evaporator coil.

This last week has been HOT here in south Texas. I've shut a lot of the rooms to save on cooling bills as I have since we moved in. Could me closing off the entire upstairs cause the system to keep dying like this? Thanks for the help to all of us! - Jeff Collins 8/7/11

Reply:

Jeff:

- leaks of refrigerant resulting in low refrigerant levels can indeed cause coil icing;

- improperly operating thermostatic expansion valve that does not meter refrigerant at proper rate can cause icing

- low air flow can cause icing - and of course several things can cause low air flow such as dirty filter or a blower fan problem

For sure, closing off part of a home is well within the normal things that a homeowner might do and in no way should it be capable of damaging the HVAC system. I suppose if someone could close enough supply registers as to greatly reduce airflow across the coil it could, however, contribute to an icing problem there.

Question: sweating on the A/C suction line

My suction line is sweating just before it enters the furnace and drips into the pan causing water buildup, therefore, shutting off my pump, and then shutting off the furnace unit. There is about 5" of pipe not insulated just before it enters the indoor unit. Will wrapping this prevent the dripping? - Sean 8/12/11

Reply:

Sean, most likely, insulating the suction line will stop condensation on its surface. You can use foam insulation tubes designed for that purpose.

A/C manufacturers recommend that the insulation be secured with plastic ties or a protective tape, and they emphasize that you should not crimp the insulation by the ties or tape since doing so will compromise its insulating value.

Question: frost on the evaporator coil, slugged compressor motor

had frost on evaporator coil and suction line. cleaned dirty coil and melted ice by turning furnace on. Turned A/C back on but only got 75F at nearest register. Did I ruin the compressor? Is there a protection device for compressor? - Greg Nelms 4/17/12

Reply:

Greg, you could be running out of refrigerant. Running the compressor briefly = may be ok, but don't keep running it since compressor motors rely on the presence of refrigerant for cooling and lubrication.

Reader follow-up:

Dan,The day the coil iced up was an unusually warm day in NJ. Wife turned A/C on in the afternoon, I did not get home till 9 PM and found the iced condition. The evaporator coil was excessively dirty {even though I change the 90 day filter every 45 days}. Temperatures here are back to normal and have not tried the A/C since that day. Afraid I slugged the compressor. - Greg Nelms 5/1/12

Reply:

Greg,

Unfortunately if the compressor was slugged, you can't un-do it. You can have the system cleaned and inspected. If the compressor is damaged it'll be noisy, or won't work at all.

Question: is frosting caused by an AC compressor with poor pumping?

evaporator fan ok and evaporator coil clean , I suspect the cause of the frosting of the suction pipe is because the AC compressor has poor pumping. - Simon Yengi Wani 5/6/12

Reply:

I don't think so, Simon. If the air conditioner compressor were not pumping or could not develop a vacuum the result would be no frost and no cooling.

Question: added refrigerant, but four days later ice was back - back to the original issue

Two weeks a go, we placed a service call for additional freon as we thought that was why air wasn't reaching thermostat setting. Service guy suspected a possible freon leak, but added 3 gallons of freon. Four days later, we were back to original issue. I checked lines running into outside unit (where fan is located) to see that there was significant ice build up. We've turned off A/C for now. I looked for filter, but couldn't find where one would be. Based on above sounds like dirty filter, faulty TEV or refrigerant leak are all potential causes. Anything else I should think of before calling a different service guy? - Brian 7/8/12

Reply:

Brian, at AIR FILTERS for HVAC SYSTEMS (article links listed at the ARTICLE INDEX the bottom of this article ) you will find a description of various places to look for the air filter on an air conditioning system - or search InspectApedia for "find the air conditioner filter"

"back to the original issue" sure suggests the problem was not cured, or your refrigerant leak is a big one; I don't like adding refrigerant to a system without finding and fixing the leak - HVAC equipment does not normally consume refrigerant.

Sometimes a tech will just add refrigerant because it's cheap and quick rather than tracking down a hard to find leak.

But 3 gallons is a huge addition - a big leak - that ought to be found and repaired.

Question: old refrigerator, chopped ice off the freezer, punched a hole in the tube

Probably not the place for me - I'm sure to get a couple laughs here but what the hell. I have a really nice old refrigerator (1945 G.E.) that was in the basement of our cafe for years. One of the staffers thought she'd be helpful chipping the ice off the freezer coils and put a hole in the tube. Enough said. I love this old fridge.

Before getting rid of it completely, I was thinking of converting it to a keg fridge and using an old dehumidifier refrigeration system. It is possible to relocate the evaporator. into the cooling space and the condenser/compressor outside without opening the lines as the fridge's top is removable.

My question is this: If I use a fan to circulate air over the evaporator coil inside the fridge and a fan on the condenser located outside the fridge, what happens to the pressures? Would this system cool the fridge and be reliable? Note that as a keg fridge, the space once cooled would not be frequently opened - hopefully preventing frost buildup etc. - Jason 7/14/12

Reply:

Jason first the refrigerant leak has to be repaired and the system properly charged. You might be able to salvage the system by soldering or expoxying the hole and having it recharged. It is difficult to solder aluminum but possible using the proper temperature and aluminum solder; epoxy is easier to try; because the freezer compartment is on the low pressure side of the system such a repair may work.

You are right that a dehumidifier is basically a chiller, but you'll probably find that the dehumidifier's operating temperature range is not designed to drop temperatures down into the range you'd use for refrigeration purposes.

...

Continue reading at UNDER CHARGED REFRIGERANT, EFFECTS or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

Or see

Or see these

Recommended Articles

• COOLING COIL or EVAPORATOR COIL
  • COOLING / EVAPORATOR COIL REPAIR
  • DAMAGED COOLING COIL
  • DIRTY COOLING COIL / EVAPORATOR COIL
  • DIRTY HVAC COIL CLEANING PROCEDURES
  • FROST BUILD-UP on AIR CONDITIONER COILS
  • MANUALS & PARTS GUIDES - HVAC - home
  • RETURN AIR, INCREASE
• DIAGNOSTIC GUIDE A/C or HEAT PUMP
• DIAGNOSTIC DETAILS A/C or HEAT PUMP
• FROST BUILD-UP on AIR CONDITIONER COILS
  • FROST / ICE IMPACT on A/C
  • HEAT PUMP OUTDOOR UNIT DEFROST CYCLE
  • REPAIRS for FROST / ICE on COIL
  • REFRIGERANT LINE FROST
• OVER CHARGED of REFRIGERANT, EFFECTS
• REFRIGERANT GASES & PIPING
• REFRIGERANT LEAK REPAIR
• AIR CONDITIONING & HEAT PUMP SYSTEMS
• WATER & ICE IN DUCT WORK
• WET CORRODED DUCT WORK

Suggested citation for this web page

REFRIGERANT LINE FROST FAQs at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.

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INDEX to RELATED ARTICLES: ARTICLE INDEX to AIR CONDITIONING & HEAT PUMPS

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