Thermostatic expansion valve schematic (C) Carson Dunlop Associates Sticking or Jammed Air Conditioner Thermostatic Expansion Valve
How to Fix an A/C or Heat Pump TEV that's not working, won't cool, warm air flow

  • TEV STICKING REPAIR - CONTENTS: repair of a jammed thermostatic expansion valve (TXV or TEV) at new air conditioner or heat pump installations. Data about & contact information for KeepRite air conditioners & Tempstar air conditioners & heat pumps
  • POST a QUESTION or READ FAQs about how to diagnose and repair air conditioning and heat pump systems.
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Sticking or jammed thermostatic expansion valves:

In addition to debris, dirt, or icing problems that occur in TEVs or thermostatic expansion valves, sometimes the thermostatic expansion valve on brand new air conditioners may need an extra jolt to get it working, as we explain here.

Page top image provided courtesy of the Toronto engineering, education & home inspection firm Carson Dunlop Associates.

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Sticking Air Conditioner or Heat Pump Thermostatic Expansion Valves at New Installation

KeepRite Air Conditioner Sticking Thermostatic Expansion Valve (C) ET InspectApediaAt TEV INSTALL & REPAIR where we list various troubles with thermostatic expansion valves and suggest diagnostic and repair procedures we noted the following:

[Click to enlarge any image]

Sticking TEV valves: The TEV and also AEVs depend on a little oil or oil mist flowing along with refrigerant to lubricate the interior of the valve.

Occasionally debris in the refigerant system can cause the TEV to jam, chatter, or fail to perform properly.

But we suspect that a more common cause of TEV valve sticking is the freezing of a droplet of water at the needle valve, holding it stuck. The valve stops working properly.

But as we learned from Ontario reader E.T. and her HVACR installation and service company, TEVs may be "sticky" right out of the box from the manufacturer. At left: a KeepRite™ air conditioner compressor / condensing unit, newly installed.

The installer used a simple "overcharge" procedure to free the TEV as we describe in this reader report.

Reader Question: new KeepRite® air conditioner not working well: does not cool the house

I placed a comment on the InspectApedia website last night about my new air conditioner not working well. Here are the photos you asked for. Our house is 980 square feet with a finished basement. I have closed all the vents in the basement.

We live in Ontario and are having fluctuating temperatures. Today it is 72F outside with an expected high of 85. I turned the air conditioner on yesterday when the outside temp was 65F and the temp inside my house was 78 because it had been a hot day and the air conditioner was not able to bring the temperature down.

I set the thermostat for 72F. It took 5.5 hours to bring the temp down to 76F, which is when we went to bed. Thorough the night it managed to bring the temp down to 72. In the morning I turned the thermostat up to 73 and the air conditioner has not stopped running, even momentarily, since I got up this morning. The couple of times I woke through the night it was running as well (I have a young baby).

I was not given a manual, only an invoice for the unit and the work done. It was installed 4 weeks ago. We had the ducts cleaned 3 years ago and they do need cleaning again - I have an appointment booked for Friday. If you would like to see the emails that were exchanged with the installer I can forward them to you. Thank you very much for getting back to me so quickly. I appreciate that I am able to ask questions this way. - E.T. 7/21/2014

Reply: why doesn't the installer fix their installation SNAFU?

Refrigerant filter drier canister on new KeepRite air conditioner installation but TEV was jammed (C) InspectAPedia ET

I see in your photos a newly installed air conditioning system that by your description certainly is not cooling. Your additional photo (left) shows that a refrigerant-drier was installed, though I can't tell from the image if it's in the right direction or not. The flow direction is marked plainly on the canister label.


Something as simple as failure to adequately clean (pull a vacuum) and filter the refrigerant system could cause the system not to cool even if the compressor and air handler themselves seem to be working.

It's usually easy to diagnose a new system by checking refrigerant charge, pressures, temperatures, and current draw. Why didn't the installing company return to fix it? Enlarging your third photograph of the data tag on the KeepRite condenser / compressor unit (shown at below left) gives us more information about this unit.

The Product model number begins with N4A318K ... which is the same as found on Tempstar® R-410A refrigerant air conditioning compressor / condenser units in the N4A3 series. These units use a Copeland® compressor and are factory-charged with R-410A refrigerant.

It's possible that your KeepRite® air conditioner is using the same equipment components, re-branded with the KeepRite® name.

Decoding the Model Data on a KeepRite® Air Conditioning Compressor / Condenser Unit

Since you were given no information whatsoever about your equipment, not even an installation/operation manual we're providing some data here.

KeepRite air conditioner data tag - similar model to TempStar series using a Copeland compressor. (C) InspectApedia

Decoding the KeepRite® product number, N4A318KC100, based on TempStar's data (cited below)

Reader Follow-up: sticking thermostatic expansion valve on new AC installations

I had the oven on for approximately 20 minutes at lunch time. The inside temp has risen and is staying at 76F although it is 72F outside and I have the thermostat set for 73. The air conditioner still has not stopped running. We have two dogs, our ducts do need cleaning as I mentioned before. But we did have it done 3 years ago.

Can this affect the air conditioner functioning to this extent? The unit is obviously working because it did finally bring the temp down through the night and maintained it this morning - but why it's struggling so hard is unclear to me.

The A/C installer did identify the problem and he came back to fix it.

I'm relaying the information that I recall from what he told us so it may not be perfectly clear, but he said the diaphragm on the TY [TEV or Thermostatic Expansion Valve- Editor] valve (??i think) was sticking on the new installs and causing it to not be seated properly.

When he contacted the manufacturer they advised to overcharge the system and force it open further, which would cause it to then close properly and seat the valve. I hope I got the information right, as this seems to be an innate problem with these units and I would hope that this information could be useful to someone else down the road.

I also want to say that I found this website just through a Google search when we were having the issues with the A/C and I was feeling desperate that something had to be wrong and was being told that it probably wasn't. You provide an invaluable service allowing yourself to be contacted with questions and providing service to others the way you do. It's a very generous thing to do and do and I, for one, am grateful that you took the time to respond. Thank you very much!

I was very glad that our install person kept coming back and looking into the issue and finally got it fixed.

Reply: Expansion Valve SNAFUs

Indeed even a small amount of dirt or debris in a new refrigeration system can foul up the thermostatic expansion valve causing it to fail to operate properly. If the installer is making an error in cleanliness during initial installation, or if s/he forgets to install the proper refrigerant filter/dryer on the refrigerant lines, or if the refrigerant charge is incorrect the TEV may jam or fail to open and close properly. Of course it's true that the TEV itself could be defective.

The result is failure to release refrigerant at the proper rate into the cooling coil in the air handler. In turn that would allow the air handler to run without adequately cooling the building.

Reader Follow-up: using a refrigerant "overcharge" to clear a stuck TEV

Our air conditioner installer installed an identical unit to ours (a Keeprite) at another customer's house this week and was having the same issues as us. He contacted the manufacturer and was told that there is an issue in that model with a valve not closing properly on installation. The unit needs to be overcharged which forces the valve open so that it snaps shut. He came tonight to do just that and it seems to be cooling.

I will be able to send more information about the specific valve etc when my husband gets home as he understands it better than I do, but I wanted to send an update to let you know that the problem has been found and in a case anyone writes in with a similar issue.

Reply: watch out for refrigerant overcharging

Watch out: The overcharge needs to be removed lest the compressor motor be destroyed.


Watch out: warranty coverage: You should register your product to assure proper warranty protection, and you should obtain the owners or installation manual for your air conditioner from the installer or if that contractor cannot help you, use the contact information we provide above to contact the company. Our search of the KeepRite websites we found did not provide links to manuals or installation guides for equipment matching your product number.

Reader Follow-up:

You had told me that the overcharge needs to be removed, so I checked and he did remove it at the time.

Company Contact Information for KeepRit®e & TempStar® air conditioning & heat pump product types & series

Reader Question: how to keep an old TEV Working on a house that was flipped and has many problems

TEV bulb position (C) Singer

I live in Quincy, IL. Be fore my mother passed away she bought me a small, cheap house that needs some repair I’m on SSI so I have a very limited income. I’m on a 2 year waiting list for the state to weatherize my house. I should have about 18 months left to go!

This house was totally redone 15 years ago by a house flipper and everything they used was, at the very best just low quality contractor type materials and they hid a lot of the problems and just made the house look pretty. It worked because a lady fell for it and bought it and it just went downhill from then.

I’ve fixed what I can since I got the house and I’m trying to hold out for that 18 months to pass to get the other repairs done but Summer is coming and I’m on three meds that make heat unbearable for me so I need my central air to be working before it gets too hot. My outside unit needs the capacitor replaced (it’s exploded at the top) but that’s a repair I can do and the cost is low.

The problem I’m having is the previous owner said that the entire AC system would run but not cool so she’d had a service tech in at some point and he found what he said was the problem and showed her husband. There’s type of thermometer type device inside the lower part of the inside unit that had corrosion on it and he told them it would be over an $80 part or he could pull it out and lightly sand it and put it back for much cheaper. So that’s what they did and the system cooled as it should again until the next year.

They did this themselves for a few years and then just stopped doing it and got window units. This device looks like a temperature probe and it’s held in with one screw. and a bracket that holds it so the probe looking part can point downward. I’d like to find out what this device is called so I can find out if I can afford to replace it. It’s obvious I can replace it but myself but not sure I can afford to buy it and I can’t find out a price without knowing what it’s called. It’s probably something very simple and I sound like an idiot by not having a clue but there’s no number or anything on it that I can find. If you can help me figure this out, I’d greatly appreciate it

I looked through all the photos on your website but I couldn’t find and pics or articles that seemed to even come close. My laptop has a very small screen and I can’t see too well so I may have just missed it. When the previous owner pointed this thing out to me they said they’d never known what it was called.

Reply: fixing a non-responsive thermostatic expansion valve - the perils of house-flipping in real estate sales

Sketch of thermostatic expansion valve or capillary tube inspection defects

I'm sorry but not surprised to read of the problems left behind when house-flippers get on to a property and perform only cosmetic skin-deep improvements. Unfortunately in real estate such problems are so widely known and, regrettably, accepted, that the burden is on the house buyer to hire the inspectors needed to have an accurate understanding of the home.

More trouble comes because a home inspection is not invasive: so if a house flipper simply laminates drywall over a horrible mold contamination problem, only an astute inspector who understands subtle clues will come to even suspect such a problem, for example by noticing that trim has been built-out or that wall thicknesses vary.

About your A/C: unfortunately I doubt that you can do the part replacement you are asking about.

** Send me some sharp photos of your AC system and of the part you describe and I can comment further, but I think that

the "thermometer" device you describe is the temperature-sensing end of the TEV or thermostatic expansion valve that monitors the cooling coil temperature and according to the temperature there, opens or closes a valve that meters refrigerant into the coil. This is an essential part of the system. If the TEV has failed the system won't cool.

To read about this device see see EXPANSION VALVES, REFRIGERANT - home

You will find a series of articles about installation and repair of thermostatic expansion valves starting with that one and continuing with TEV INSTALL & REPAIR.

If cleaning the sensing bulb and clamping it back in place doesn't get it working, sometimes a service tech will try adjusting the TEV itself - SOME (not all) models have an adjustment screw in the unit base. But watch out: one cannot make an accurate adjustment without using some monitoring equipment that looks at temperature and at refrigerant pressures.

To replace the valve requires opening up refrigerant lines, and to do that requires removing the refrigerant from the system using a refrigerant-recovery machine (we don't just dump those gases into the air), followed by the valve replacement, followed by installing a new refrigerant charge in the system.

All of that work will cost probably hundreds of dollars: the $80. part is probably for the TEV itself but doesn't include the labor nor the refrigerant.

Try cleaning the sensor. If the system won't cool, ask your local air conditioning service company if they can perform a low-cost diagnostic inspection to tell you what the system needs to operate.

If all of the repair costs are significantly more than the cost of a window air conditioner, you may want to consider installing a window A/C as a temporary measure.

Keep me posted.


Continue reading at TEV INSTALL & REPAIR - the air conditioning system seems to be "running" but not enough cool air, or no cool air at all is being delivered to the occupied space. or select a topic from the More Reading links or topic ARTICLE INDEX shown below.



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TEV / TXV STICKING REPAIR at - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.

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