InspectAPedia®

Photograph of attic air conditioning air handler, condensate drips on floorA/C Cooling Coil Diagnosis & Repair FAQs
Set 2 of Q&A on coil icing, leaks, repairs

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A/C & heat pump cooling coil /evaporator coil problem diagnosis & repair Q&A:

These additional questions & answers help troubleshoot evaporator coil or cooling coil problems such as blockage, frost or ice formation, reduced air flow or other cooling coil issues.

This article series discusses the diagnosis and repair of cooling coil or evaporator coil problems that occur in the air conditioning or heat pump air handler unit such as frost or icing, dirt, blockage, refrigerant leaks, or improper sizing. Our photo at page top shows the cooling coil in the attic air handler component of a central air conditioning system.



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Cooling Coil (Evaporator Coil) Diagnostic Questions & Answers

Schematic of an air conditioning cooling or evaporating coil (C) Carson Dunlop AssociatesThe cooling coil or evaporator coil is where building indoor air cooling actually takes place.

[Click to enlarge any image]

A cooling coil which is blocked by debris or ice and frost, or which is damaged can obstruct air flow and reduce air conditioning system output. The air conditioning system evaporator coil and problems include ice and frost build-up, dirt or debris blocking air flow through the coil, and damaged or leaky cooling coils.

These questions & answers about ice or dirt blockage of the cooling coil or other evaportor coil troubleshooting were posted originally at DIRTY COOLING COIL / EVAPORATOR COIL or at FROST BUILD-UP on AIR CONDITIONER COILS - you'll also want to see the diagnosis and repair suggestions in those articles.

Question: why is the coil raining water droplets?

(May 27, 2011) DEVIN said:

What can cause an evaporator coil to rain droplets of water , the water is not running down the coil but falling off. Very little but enough to make a puddle a day. The coil has been cleaned several months ago. And has a proper trap , and seem to have plenty of air flow

Reply:

It is normal for moisture to collect on the evaporator coil during the cooling cycle, as moisture condenses out of warm moisture-laden air onto the evaporator coil (cooling coil) surface.

If that condensate is not being properly drained, however, the drain system needs repair lest you have a leak into the building.

Question: air coming from duct is not blowing enough cool air

(June 1, 2011) Y Riggans said:

Air coming from duct is not blowing cool enough air. Temp inside with central air on was still at 85 after 2 hrs and temp outside was extremely hot today 6-1-11. Worked up until today!

Reply:

If air is coming out of supply registers at a good rate but the air is never cool then your system is not cooling. Common causes are lost refrigerant or a refrigerant metering device (thermostatic expansion valve or cap tube) that is not working. Check out the LOST COOLING CAPACITY diagnostic article linked to at page left.

Question: Fan on AC unit stopped working

(June 15, 2011) Rod said:

Fan on A/C unit stopped working, replaced capcitors, fan is still not coming on I can hear the condenser coming on any ideas?

Reply:

Rod:
If you are talking about the fan in the indoor air handler unit, there could be a problem with the fan limit switch. Check your fan limit switch to see if there is a manual override or "ON" button. On some units this is a white knob that protrudes through the fan limit switch cover. Push or pull the switch to force the fan to "ON" - if that switch is present and you can't get the fan to run, and the capacitor is good, the problem may be a bad switch, motor, or electrical connection.

Question: Replacement A-Coil (cooling coil) was too small?

(July 18, 2011) David said:

If our a-coil was replaced by one not large enough would that cause our cooling not to be good enough when the it is very hot outside? Ours was replaced because it was leaking and now when it is very hot outside it wont cool the house more than into the 80's. Year before that we had a new outside condenser unit put in.

Reply:

David: if the new A-coil in your indoor air handler is significantly smaller than the one that was taken out, it may be that it's not providing enough cooling surface for the volume and rate of air being blown across it. Take a look inside the air handler to see if there seems to be a larger (than before) space through which air moving through the air handler is actually bypassing the cooling coil and ask your HVAC tech about that observation. Let us know.

Reader follow-up:

The a-coil is a little smaller but supposed to be ok for our 3 ton system. The tech said no leaks but added 2lbs of freon (10 months since last added). Said our compressor valves were bad because of noise he heard. Payne compressor only 3 years old. Replaced compressor but hasn't been hot enough to see if it made a difference.

Reply:

David, an HVAC tech that added two pounds of refrigerant after one year of system use and told you that there are no refrigerant leaks leaves me mystified. Unless your system was short-charged in the first place, having to add refrigerant always means that we've lost refrigerant from a leak.

Take a look at the article linked on this page at Continue reading where you will find an INDEX to RELATED ARTICLES that includes a live link for REFRIGERANT CHARGING PROCEDURE
You'll see that in a residential air conditioner or heat pump the exactly correct amount of refrigerant is important for effective and efficient system operation.

Question: Air handler stops and stdarts too often

(July 22, 2011) Bill said:

My air conditioner goes off and my air handler stops and seconds later comes back on. This will continue for several minutes before it shuts down. Any ideas of problem?

Reply:

Bill an air handler that stops and and starts very frequently - seconds apart - sounds like a thermostat or control board problem.

Question: intermittent delivery of cool air

(July 23, 2011) Marc said:

Our central air runs when we turn it on, but sometimes it blows cool air and sometimes it doesn't. Sometimes the air pressure is strong and sometimes it not. Sometimes the air will blow for 30 min and sometimes 3 hours. On a good day it doesn't seem to cool the house past 78 degrees. The last 2 days in the upper 90's the ac would run, but there was little to no air pressure coming out and if there was a little air pressure coming out, it was not cool air.

Our indoor house temperature read 85 degrees. Today it is blowing hard and the air is pretty cool, but seems to still take a while to cool the house down and doesn't get below 78 degrees (It is about 90 degrees out today outside). I think the air coming out should be cooler as I have been in other houses with central air that are cooler. We have had this problem the past 3 summers.

We had a guys take a look and he said it could be a small leak somewhere and he just recharged the system. I don't want to call out the guy again if I don't have to. Could the problem be a leak still or something else because it works semi properly inconsistently. Any help would be greatly appreciated. Thanks.

Reply:

I'd look for a control problem or an automatic duct damper problem since you note that when the system runs it's cooling capacity is satisfactory

Question: Condensate doesn't drain when blower is running and overflows drain when blower stops

(Aug 3, 2011) Mark said:

I have a horizontal fan/coil unit that wont let the condensate drain while the blower is operating and when the blower shuts off , the water comes out faster than the drain can handle it and overflows the pan

Reply:

Mark it sounds as if there are two problems:

1. you may be getting condensate blown down the ductwork during system operation

2. your condensate drain is clogged or undersized and the pan may also be undersized.

I'd ask an HVAC tech to look at and correct both problems, though first you might see if you can clear your condensate drain yourself.

Question: Lennox heat pump compressor locked up

(Aug 18, 2011) David S said:

In December of 2010 my Lennox heat pump compressor “locked up” and my service tech Larry Luker gave me two options

1) replace the faulty compressor

2) replace the entire outside unit and air handler unit evaporator coil. Because the existing unit was 10 years old I opted to replace the unit and evaporator coil.

The home is a three level townhouse with HVAC zone control and I never had any real problems with heating or cooling before this event. Once the unit was replaced the heating cycle worked fine and we had a mild spring and I rarely used the cooling cycle.

I got married in April and in mid May we rented the unit to a nice couple. Just after they moved in the weather turned hot, very hot and the AC started to act up.

The unit would cut off and not restart for extended periods of time and we would call our service tech and he would come over and say that the thermostats were’t in sync or there was a stuck bulb in one of the thermostats or the unit was low on freon, the unit was froze up because the thermostats were’t all set the same, or there was a problem with the zone board etc etc.

All in all he made about seven or eight trips and in desperation we had the zone board and all the thermostats replaced, the freon topped in hope to eliminate the real issue.

The unit would eventually fired back up and run for 5 or 6 days and then cut off once again. Finally the compressor just refused to start but when it did attempt to start the circuit breaker that feeds the outside unit would buzz (not trip just buzz).

The tech put a hard start capacitor on the unit to get the compressor to start but when it did start it sounded like it had a bunch of bolts rattling around in side. Our tech call Lennox locally and they said that all they could do is give him a replacement compressor (they only had one left so it sounds like this may be a bad run or design).

I called consumer affairs and pleaded for a new unit but the person on the phone told me that all Lennox would do is “furnish a replacement compressor”. I ask to speak to a supervisor and held for one hour and got cut off, I called back twice and left two messages and never got a call back.

When we took the door off the air handler to get the nomenclature off of the new evaporator coil we found found that it is substantially smaller that the original coil and I thinking that this could be the reason the unit keeps freezing up.

Our tech put in the new compressor and the unit ran for a week and now it is down again. This unit has cost us well over $10,000.00 now and we still don’t have a reliable HVAC system and will probably loose our tenants and they will potentially take legal action against us.

Reply:

David S
Sounds like there is a problem with zoning system causing system to freeze and the system is also overcharged causing the noisy compressor and compressor not to start. Compressor is pumping liquid when it starts and it is designed to pump only gas.

Question: intermittent start up problems at air handler

(June 3, 2012) joe g said:

After I turn my a/c unit on sometimes my evaporator unit will turn off then on again maybe once or twice or sometimes never?? While the compressor would be running with out going off .

Reply:

Look for a control problem, wiring short, or failing start capacitor

Question: inadequate cool air supply

(June 14, 2012) Dan said:

My air conditioner blower motor is running but there is inadequate air flow coming through the vents, this just started today and was running fine prior

flag like

Reply:

June 17, 2012) Anonymous said:

check ur filters Dan and the inside coil/evaporator and see if it's dirty

Editor adds:

Thanks Anon, we agree completely. When airflow in an air conditioning system is inadequate the place to start is with a dirty air filter.

Other sources of reduced airflow include:

a dirty blower fan assembly
damaged, leaky, or crimped ductwork
an electrical problem causing slow fan speed
iced cooling coil

Question: Don't confuse a dirt-blocked coil from ice or frost formation on cooling coils

I cleaned the outside unit by removing the panel and the fan which was attached to some wires. I didn't disconnect or damage anything. I collected 1/4 a garbage bag with the dirt and debris found to the bottom. In attempting to clean the inside unit and fan, I noticed lots of ice on a grid like thingy and some tubes or lines.

The inside however looks to be pretty clean but I will wipe it down anyways. I purchased this house in 2006 and so far had to change the compositor battery looking thingy professionally.

2 years ago but still have freezing when it is about 100 degrees outside or more. What else could I do? How do I know if I need freon or refrigerant and where does it goes? Please help ...thank you! - Pamela 6/10/11

Reply:

Pamela it sounds as if you are describing frost and ice formation on the cooling coil (evaporator coil) inside the indoor air handler unit.

Icing coils are caused by low air flow (dirty cooling coil, dirty air filter or duct defects) or by a low refrigerant charge. Adding freon is something that needs a service call from a trained HVAC technician - it's not something a homeowner can or should try to do.

While ice or frost on on the coil could be caused by a dirty coil, the technician needs to defrost the system and inspect the coil as part of diagnosing and fixing the trouble. If on defrost (just leave the system turned off for an hour or so) shows that the evaporator coil is actually clean, then the problem is elsewhere in the system and you'll want to see the diagnostic advice at FROST BUILD-UP on AIR CONDITIONER COILS.

Question: air conditioner coils still freeze up after cleaning with water

My air conditioner coils and fins are still freezing or icing up after cleaning them with water ...could there be something else wrong that it still freeze or ice up? I have to turn on and off the A/C 's thermostat every 15 minutes or so just to melt the ice and for it to cool up again. anything else i can do to fix this problem? - Jack 10/20/11

Reply:

Jack,

if the A/C or heat pump cooling coil is clean and air is flowing across it but it's icing, then I suspect that there has been either a loss of refrigerant (low refrigerant can cause icing at low charge until there is simply too little refrigerant left in the system, then no icing and no cooling)OR there is a problem with the refrigerant metering device such as a sticking thermostatic expansion valve.

Either of those diagnoses and repairs will need a service call from a trained HVAC tech. Keep us posted - what you learn will help other readers.

Question: odors when switching from heating mode to cooling mode

(Apr 1, 2014) Bruce l. said:
I have one year old heat pump unit and the only problem is when I go from Heat to a/c the indoor unit gives off a very odd oder. Not when I go from a/c to Heat.

Reply:

Bruce let's think about what's different switching from heat to A/C vs A/C to heat. Typically the same blower fan, ductwork, and air registers are involved in both modes. What's different is the direction in which refrigerant is circulating inside the system - not something that would explain an odor difference.

Also different is that in cooling mode you're probably producing condensate, perhaps operating a condensate pump. I'd look at that system to start.

Also different when switching from AC to heat is temperature at the coil.

Question: HVAC fan on continuously to help defrost an iced-up cooling coil?

Will leaving the HVAC fan on continuously help defrost an iced-up cooling coil?

Reply:

Tony:
Yep, leaving the fan on all the time is using the fan to help "defrost" the icing coil. But you still don't want coil icing - it's wasting energy and interfering with the cooling system. Your A/C guy is right that a faulty TEV (thermostatic expansion valve) COULD be the problem but also there could be other causes (dirty filter, blocked air flow, or low refrigerant level).

Question: can a clogged condensate drain cause the evaporator to freeze-up?

(Feb 23, 2015) Bob Mann said:
can a clogged drain pan under the evaporator cause the evaporator to freeze up?

Reply:

Bob I don't see a connection between a condensate drain pan clog and a frozen evaporator, except for a rather indirect one: if the cooling coil is very dirty that dirt can block air flow and lead to a coil frosting or icing problem. If it is really dirty maybe some of that crud has fallen into and clogged a condensate drain.

(Feb 27, 2015) Bob Mann said:
thank you, I did clean it out, the water was about an inch above the base of the evaporator? It hasn't frozen up since I cleaned it. The filter was clean, maybe just coincidence. There was good water flow, I'll see what happens. Thanks again

Reply:

If you get recurrent icing problems on the evaporator I'd take a look at FROST BUILD-UP on AIR CONDITIONER COILS

Question: cooling coils on HVACR equipment in a cement company environment

What should be the recommended fin material and fpi for condenser coils in cement company enviroment?

Reply:

Matthew,
to specify a cooling coil fin material you'd want to list the corrosive ingredients you expect to be in the air.

Caustic dust is one possibility but there may be others. With that information I'd call the HVAC manufacturer to ask their advice. I suspect you're looking at a lower heat transfer rate and using stainless steel, or going with a conventional coil and water-washing the outside unit.

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: 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 "More Reading" links at 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: AC blows cold air but won't reach set temperature - could it be the thermostat?

our a/c is blowing cold air but temperature will not reach to what i set on thermostat. thermostat reads 79, and even when i set it at 74 or 75, it never gets cooler than 78. this was also on a day it was 105+ outside. a/c was just serviced 2 weeks ago and reported in perfect working order, but thermostat was recently replaced. i don't THINK something is wrong with the a/c system, but is it possible the thermostat could be malfunctioning and causing these problems? any thoughts? - Alex 7/11/12

Reply:

Alex,

The thermostat is basically an "on-off" switch. If it's calling for cooling and the room temp never reaches the set temp on the thermostat, the problem is not likely anything to do with the thermostat. Only if the thermostat fails to respond to room temp would I think otherwise.

Depending on the size and condition of your cooling system, its installation details, duct work, capacity, and similar factors, in a home with high heat gain in very hot weather, the system may be unable to reach the set temperature.

Your hvac service tech would probably check to see if the system is producing cool air at a normal temperature and that the air flow is not blocked or reduced by a defect such as a dirty air filter or cooling coil or duct defect.

Question: Can a dirty cooling coil cause HVAC system vibration? Also the service policy & warranty I purchased is not being honored by the service company.

I have a question concerning the A/C unit. When the A/C Unit turned on (inside furnace located in hallway) had a noise (vibration on the A/C Unit) I have a warranty plan and they send a technician.

Technician checked the blower by sliding the blower from its position and stated blower was OK. Technician went on and check Other parts of the furnace and was unable to determined what was causing the vibration. He had a device (camera) to check inside air handler and notice that the coils were dirty.

He stated that it is possible that dirty coils (A/C Unit still operating OK) could cause the vibration on the unit. Technician stated that A/C unit must be pulled/removed from its location in order to clean the Coils, which would cost over $1000.00 to include cleaning coils plus the labor.

Unfortunately the Warranty plan does not cover cleaning the Coils (maintenance), the Warranty Company interpretation of dirty coils is "Clogged coils", which technician stated coils were not clogged just dirty.

My question is: Could dirty coils (unit still cooling & running OK) can cause the vibration? R.V. 5/11/12

Reply:

The assertion that a dirty coil caused the unit to vibrate leaves me baffled. How did the tech explain that?

Indeed if the coil is really dirty and blocked it may frost over or fail to pass enough air and your cooling air will be reduced, but that's not vibration.

Look for loose parts that move when motors or fans run, including a bad blower fan bearing, mounts, loose duct work, etc. Try pressing gently on components to see if the vibration stops - DO NOT GET YOUR FINGERS CUT OFF IN MOVING PARTS - so you may want to have a more qualified tech take a look.

Reader Follow-Up:

Thank so much for your response. As I mention on my email below that the Warranty plan does not cover cleaning the Coils (maintenance), and their interpretation of the technician report that vibration is because of dirty
(clogged) coils.

I complained to the Customer Service Rep that the technician DID NOT correct the vibration problem and was not sure what Was causing it. Customer Service Rep suggested to contact the technician and re-submit a report on what could be causing the vibration.

I did contacted the technician, and explained to him that Customer Service denied the claim because of his report stating that the coils were 100% dirty. The technician contacted Customer Service but the claim was still denied based on this report.

As I stated to customer Service and the technician that the Vibration was not FIXED, I still have to PAY $75 Deductable (service Fee) and the vibration problem was not fixed.

My conclusion is that the technician stop searching to determined what was causing the vibration after he saw that the coils needed to be clean and stated that could cause the vibration and he stated that it should be cover under the warranty (technician estimate cost for cleaning the coils $850.00 submitted on his report).

Again, I mention to the technician that he did not fix the vibration problem. I did read the Warranty Plan and it states that cleaning of the coils is not cover under the plan, but my point was to customer service and technician that the vibration problem was not fix. Again, thank you for your response. 5/31/12

Reply:

You can inform the customer service people that a dirty coil blocks airflow but does not cause vibration in the system. I would ask that a more qualified, experienced tech be sent to the job. It sounds from your description as if the tech you had knew that he could blame an excluded item and thus escape honoring the warranty.

Reader Follow-Up:

I agree. When I spoke to the Customer Service Rep, I clearing stated that the A/C Unit was working Ok and the technician verify that A/C air flow/cooling was working ok.

Bottom line is that Customer Service Rep concluded (their interpretation based on report) that warranty plan does not cover dirty coils, and totally ignored the vibration problem.

Do you have an idea about how much (an estimate) it would cost to get the coils clean? I as mention on my previous

Email that the technician estimated about $850 (to include 4 labor hours), he claimed that the entire unit must

be remove and remove all panels in order to the clean the coils, and if it took more than 4 hours, it could cost

more around $1000 to complete the job. I told him he was just cleaning coils not replacing the coils.

Reply:

I would not touch the coils before seeing myself that they are actually dirty and blocked with debris. This whole transaction sounds suspicious. I'd like to see some well-lit sharp focus photos of the cooling coil. Also, when the time comes to clean the coils, there are procedures for cleaning in place.

Reader Follow-Up:

The technician had a device (about two feet flexible tube with camera at the end) that he insert inside the area where the coils are located, where it shows the coils were dirty. I am sure the coils in any A/C unit after Long period time (5 to 7 years) could get.

I know for a fact that during a semi/annual A/C checkup or Service the technician don't inspect the coils, they just conduct an external checkup.

I agree with you that the whole transaction sounds suspicious to me also.

The company(where technician work for) make a quick $75 and Warranty Plan did not have pay for it.

Reply:

It's a disturbing topic - too often in the news we read reports of companies that sell insurance but who pull out all the stops to resist actually paying on a claim. As you describe no ready access to the cooling coil, cleaning would require cutting and making a (reusable) access cover for an appropriate side of the unit; there are procedures for cleaning the coil in place that should be much less costly. If you choose that approach take some photos and send them along and we may be able to offer other comment.

Please keep me posted on how things progress, and send along photos if you can. Such added details can help us understand what's happening and often permit some useful further comment. What we both learn may help me help someone else. - Ed. 6/2/12

Question: can a bad fan capacitor cause cooling coil frosting?

A tech replaced the dual run capacator on the outside unit of my heat pump system. The fan would not spin and he needed help over the phone to get the unit running again. Could an improper installation of the dual run capacator cause frost and icing? Previous to his visit I never had a problem with frost or icing. - Mike 5/24/12

Reply:

Mike, maybe in some way I don't fully understand. The fan on the outdoor comprressor/condenser cools the outdoor half of the system and thus permits condensing high pressure high temperature refrigerant back to a liquid form.

One would think that if the refrigerant didn't condense back to a gas it would not be properly metered into the indoor cooling coil and I'd guess that the result would be reduced cooling, not more cooling.

Usually an iced coil results from

- slower air flow across the indoor coil because of a dirty air filter or fan unit or an indoor blower fan that is not working properly

- a problem with the refrigerant metering device (TEV)

- low but not zero refrigerant in the system

In the link at the "More Reading" links at the bottom of this article under COOLING COIL see the article FROST BUILD-UP on AIR CONDITIONER COILS where we list other causes of coil frosting such as a dirty air filter or lost air movement capacity due to dirt build-up on the air handler's blower fan blades.

Let us know what your tech finds - it will assist other readers

Question: frozen coils, no air flow, found low refrigerant, added refrigerant, coils frozen again

(I have a very old Rheem) Frozen Coils with no air flow Saturday and Tech found little over a 1 lb low on R-22. Sunday better air flow not cooling, tech found he overcharged and removed R-22. System ran normal for 3 days.

Thursday coils froze and tech (new tech, same company) found low and added.. ran normal. Friday morning awoke to find no air flow and coils frozen again. Turing off AC and the fan on has melted the ice and air flow is restored.

Both techs were hesitant to look for leak with dye- and suggested putting that money into a new unit.

I know the unit is old- but am I crazy to try to find the leak? Compressor is a little noisy- but it has been that way the 6 years we've lived here.. and doesn't seem like it would cause loss of refrigerant. To get this fixed over the Holiday weekend- and quickly- I went with a company I have never used- so I'd love a second opinion. - Scott 7/8/11

Reply:

Scott:

Quite so: too much OR too little refrigerant can cause icing in the system. If it were me I'd ask the techs to find and fix the refrigerant leak. A leak in refrigerant lines in a system that is otherwise working fine is no reason to replace the equipment itself. And surely finding and fixing a leak in tubing is cheaper than replacing the whole system.

An exception to that view is if inspection discovers that the evaporator coil is so badly corroded or so much of other systems are so badly corroded that leaks are likely to be everywhere and recurrent - in that case it's time for a more extensive replacement.

Question: evaporator coil and suction line keep freezing up

I have a 2005 Duroguard A/C hooked up to an old GE gas furnace. The evaporator and suction line freeze up constantly. Tech checked high side pressure only, it was good. Furnace blower motor, capacitor and filter were replaced and the unit still freezes. The thermostat works normally. I am beginning to suspect a bad TEV or cap tube. Does that sound like the problem? - Chuck 7/8/11

Reply:

Chuck: indeed if the refrigerant charge is correct and airflow across the coil is good but icing is still occurring, I'd suspect a bad TEV.

(Thermostatic expansion valve). Some TEVs are adjustable. And a TEV can be clogged or blocked by dirt, debris, or ice.

Question: ice formation at the point of entry to the cooling coil

I have a 20 yr-old amana ac unit, that is freezing at the point of entry, the hose into the furnace, a small coil of ice. It had been serviced last year with an addition of freon and a good hose down to improve air flow.

This year another good hose down after it slowed down and couldn't keep up. Now it won't keep up again, set at 74 and seems stuck at 77, checked and that's when I saw the ice. Have a dehumidifier in the furnace room going.. any thoughts? - Martha 7/19/11

Reply:

Martha, ask your service tech to check for a refrigerant leak or loss and also for proper functioning of the thermostatic expansion valve.

Question: persistent ice formation on the cooling coil, letting it melt off doesn't fix anything

My small apartment AC does not sufficiently cool my place. The thermostat is set on 75 and the temp is around 83 (I live in a very hot, dry climate).

There is ice/frost on my coil and so I called a repairman who told me it's because I have set the temp too low and "it will never be 75 degrees in here" and told me to turn off the unit until the ice melts, and to change my filter, then he left.

I changed the filter and the day after it's iced over again and still not cooling down. Should I call him back and have him check for something more specific this time? - Daisy 7/25/11

Reply:

Daisy, if the coil is frost-covered that means that either the air flow across the coil is blocked or reduced (say a dirty air filter) or the refrigerant charge is low (leak) or the refrigerant metering device is not working properly.

The advice from the repairman was a gift to you in that it's good starting advice and was probably free.

But now that we don't think the airflow is blocked and you've changed the filter, you need a service call to diagnose and fix the icing problem. If the unit's fan is working properly and moving plenty of air then I suspect a refrigerant problem.

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. T

he 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.

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