Symptoms of bad txv 410a

Using the previous examples comparing the operating pressures of an R-22 system to an R-410A system, the R-22 system would have a compression ratio of 3.02:1, while the R-410A system would have a compression ratio of 2.98:1. The actual efficiency gains from R-410A are due to its superior thermodynamic values over R-22.

Symptoms of bad txv 410a. Symptoms. A stuck open TXV will flood and freeze the evaporator core, possibly damaging the compressor with incompressible liquid. A stuck closed TXV will leave an evaporator starved of refrigerant and the compressor deprived of its lubricating oil. Troubleshooting the TXV valve or thermostatic expansion valve and its location and the ...

Highlights. It costs an average of $400 to replace the TXV expansion valve on an AC unit. The average cost is $350–$450, but it can range from $100–$700. The labor and the valve are typically the only …

2. Common Symptoms of a Faulty TXV in HVAC Systems. High or low suction pressure. Low superheat or high subcooling. Compressor overheating or short cycling. Uneven cooling or heating. Ice ...2. AC Compressor Constantly Running. Another common symptom of a bad expansion valve is that the AC compressor will constantly run. This can be caused by low refrigerant levels, which will put extra strain on the compressor, or by a leaking valve, which will not allow the refrigerant to enter the evaporator properly.Jun 24, 2011 · Forum Rules. I have a 3Ton Carrier Heat Pump unit using 410A that has extremely high suction pressure around 250PSI. I also have a low liquid line pressure around 300PSI and my sub-cooling is around 40-50 Degrees. I have checked for a stuck liquid line solenoid but this system does not have one, and I checked the reversing valve and its ... And R410A is the most common substitute for central air conditioning and heating split systems – an outdoor AC or heat pump and an indoor furnace or air handler. R410A is a hydro-flurocarbon (HFC) and is safe for the ozone layer. ODP = Zero. Puron is a brand of R410A developed by Carrier, and for some, the name is synonymous with R410A.The TXV is a metering device that restricts the flow of refrigerant. The TXV measures and adjusts to maintain a specific superheat. It does this by using three pressures. TVX Bulb Pressure (opening force) …

Nov 16, 2021 · Coolant systems are complex, and maintenance generally requires complete teardowns of the units in question in order to access the parts that need to be changed. It costs an average of $300 to professionally replace a TXV valve, or as little as $100 if you do it yourself. Labor costs $150, on average, but it varies based on your location and ... First, measure the superheat right at the evaporator outlet in the same general location as the TXV bulb and equalizer. In most cases, the superheat at that point should be 5-10 degrees, but refer to the manufacturer's specs when in doubt. In some cases, you will not have a pressure port at the evaporator, so you must rely on a pressure reading ...Sorry - thought I had already answered. Outdoor unit and blower are both Trane and new install in Q3 2012. - Outdoor: 2.5 Ton Heat Pump (Model# 4TWB4030G1000AA) - Air Handler (Model# GAF2A0A24S21SAA) I'm not getting elevated pressure during cooling so not sure how a blockage or airflow issue would show during …Suction went sky high to 500psi and the high side went down about 15psi. This melted the ice on the coil and txv and ran the unit back in cooling mode. First thing I saw was that the TXV started freezing up under the core of it. Double checked everything, I assume that the TXV was bad.The TXV also needs a proper pressure drop (about 100 PSI); without that pressure drop, the TXV can't do its job properly. When the suction pressure is low, the technician should take the subcooling and superheat inside and outside. The goal is to look for the temperature differences between the inside and outside measurements.Aug 27, 2003 · Symptoms of this overcharged system include: High discharge temperature. High condenser subcooling. High condensing pressures. Higher condenser splits. Normal to high evaporator pressures. Normal superheats. High compression ratio. High discharge temperature: With an overcharged system, the high discharge temperature of 240 degrees is caused by ... 410a low suction pressure. I injected super seal in a 410a system that had a tiny leak that I could not find. 2 years later I come across the problem of low suction pressure normal head pressure. Replaced txv and had same problem. Replaced compressor and had the same problem. Could the super seal be clogging the txv or …

How to use superheat and subcooling measurements to diagnose what’s happening inside the refrigeration circuit.Jun 24, 2011 · Forum Rules. I have a 3Ton Carrier Heat Pump unit using 410A that has extremely high suction pressure around 250PSI. I also have a low liquid line pressure around 300PSI and my sub-cooling is around 40-50 Degrees. I have checked for a stuck liquid line solenoid but this system does not have one, and I checked the reversing valve and its ... One of the primary bad TXV valve symptoms is inconsistent cooling or heating in different parts of your home. The TXV valve helps in the equal distribution of refrigerant, which in …Liquid-line solenoid valves. It is common practice to select liquid solenoids for a pressure drop equivalent to a 1° change in saturation temperature. For R-22 at 100°F, this is about 3 psi. If the same criterion is used for 410A, that is a 1° loss in subcooling; the valve would be sized for about 4.75-psi pressure drop.The symptoms of a bad TXV include high superheat, low superheat, high subcooling, low suction pressure and low head pressure. However you might need to take additional diagnostics steps to rule out other factors that can cause similar symptoms How does a TXV valve work?May 5, 2016 · Bad TXV. Not necessarily low on charge. Many times I've had normal subcooling and a ll restriction. The subcooling skyrockets when some knucklehead jams a bunch of refrigerant in it to get the suction pressure above freezing. If it's a copeland compressor from 2014 I can almost guarantee the TXV needs some of the magic miracle additive ac renew

Rhoback dog.

Let’s look at the pressure/temperature correlation of R-410A on the P/T chart above. At 118 PSI, the saturated temperature of R-410A is 40 °F. At 318.5 PSI, the saturated temperature is 100°F. ... of setting the system based on vapor pressure is much worse and kind of laughable when it comes to systems with a TXV as the metering device. As …An R-22 evaporator running at 40F saturation temperature will have a corresponding pressure of 68.5 psig. Should the suction pressure drop below 57 psig, the coil temperature will drop below 32F causing moisture in the air to freeze on it (see Figure 4) causing no end of trouble. A R-410A evaporator running below 100 psig will freeze-up …There are many reasons why an expansion valve may suddenly go bad. Sometimes the parts are just defective. Other times clogging in the system will damage the part. In many cases, the part simply deteriorates due to age. Regardless of the cause, fixing a broken expansion valve can be challenging and should only be undertaken by a professional.How to use superheat and subcooling measurements to diagnose what’s happening inside the refrigeration circuit.

TXV’s control the superheat. You can, however, check the superheat to see if the TXV is working properly. To Determine Sub-Cooling: 1. Take the high side pressure and convert it to temperature using chart or gauge. 2. Then take the temperature of the liquid line as close to evaporator as possible before the metering device. 3. Take the difference between the …153 Post Likes 410A TXV Troubleshooting I am a fairly new tech so bare with me, went to a service call earlier today for no cooling on a 410a system. Air filters were …Aug 12, 2013 · 153 Post Likes 410A TXV Troubleshooting I am a fairly new tech so bare with me, went to a service call earlier today for no cooling on a 410a system. Air filters were clean, so went upstairs in the attic to find that the TXV was frozen over and the indoor coil was frost over some. The Blower was running great as it was passing thru the coil. 410a system. Txv. Low subcooling. High superheat. Figured it was low, put about 3 pounds in and subcooling never went up, super heat went down. Temp dif was better, but not great. I was thinking I had a restriction or bad txv, but I’m still learning and didn’t really have a clue.Highlights. It costs an average of $400 to replace the TXV expansion valve on an AC unit. The average cost is $350–$450, but it can range from $100–$700. The labor and the valve are typically the only …Symptoms of this overcharged system include: High discharge temperature. High condenser subcooling. High condensing pressures. Higher condenser splits. Normal to high evaporator pressures. Normal superheats. High compression ratio. High discharge temperature: With an overcharged system, the high discharge temperature of 240 degrees is caused by ...TXV KNOWLEDGEIn cooling operation a bad Thermostatic expansion Valve could cause the suction pressure to drop to 0 PSIG It could cause the head pressure to r...TXV troubleshooting tips. TXV troubleshooting tips. Wednesday, March 1, 2017 Be social | Take part Keep me updated. Markets we serve; Automotive Buildings - …Thermostatic expansion valves (TXV) are responsible for metering the proper amount of refrigerant into an evaporator coil. When they fail, they either cause the evaporator to be flooded (overfed) or starved (underfed) for refrigerant. This can be observed by measuring the superheat value of the refrigerant as it leaves the evaporator.Another common reason for overcharging a system, causing AC high-side pressure too high, is too much refrigerant(R134a, R410A). Additionally, there may be too much oil in the system. ... and potential system shutdown are the main symptoms of bad TXV. To conclude, that was all you needed to know when you face AC high side …R-22, R-410A Refrigerants! Checking the Charge- How to tell if there is a Restriction or Bad TXV!This is how to figure out if a TXV is not letting enough Ref...No cable box. No problems. Dismiss Refrigerant Charging: What it looks like to have a Bad TXV Compared to just a Low Charge!This is a system that is actually is charged properly but I am...

Bad breath is a common problem — everyone has it from time to time. When you’re worried about how your breath smells, it can make you feel self-conscious and get in the way of socializing. And bad breath can be a sign that your teeth, gums ...

You can use the OEM valve for the evaporator coil if it is available or you can use a Parker Universal A/C or heat pump TXV. Select the valve you need: 1½ - 3 ton R22. 3 - 5 ton R22. 1½ - 3 ton R410A. 3 - 5 ton R410A. Select the correct adaptor to fit the existing coils connection: Aeroquip, Chatleff or mail flare.Let’s look at the pressure/temperature correlation of R-410A on the P/T chart above. At 118 PSI, the saturated temperature of R-410A is 40 °F. At 318.5 PSI, the saturated temperature is 100°F. ... of setting the system based on vapor pressure is much worse and kind of laughable when it comes to systems with a TXV as the metering device. As …Highlights. It costs an average of $400 to replace the TXV expansion valve on an AC unit. The average cost is $350–$450, but it can range from $100–$700. The labor and the valve are typically the only costs associated with this project. This is a difficult project to DIY, so leave it to a pro.The charge used in a 410A valve bulb runs higher pressure because it is opposed by the pressure of the Equalizer port running at 410A pressures. The port sizes are usually not much different if at all. In the case of our Sporlan valves the port sizes are the same between 410A and R22. Scenario 1: 410A valve on an R22 system.Using the previous examples comparing the operating pressures of an R-22 system to an R-410A system, the R-22 system would have a compression ratio of 3.02:1, while the R-410A system would have a compression ratio of 2.98:1. The actual efficiency gains from R-410A are due to its superior thermodynamic values over R-22.Using the previous examples comparing the operating pressures of an R-22 system to an R-410A system, the R-22 system would have a compression ratio of 3.02:1, while the R-410A system would have a compression ratio of 2.98:1. The actual efficiency gains from R-410A are due to its superior thermodynamic values over R-22.Jun 22, 2020 · Check subcooling at the outdoor unit and verify correct charge. You need to have a solid line of liquid delivered to the TXV for it to do its job. Get the charge set first by subcooling before overanalyzing valve operation. Confirm TXV bulb is properly attached and insulated. This procedure should be done with a factory brass or copper strap or ... When a Good TXV Goes Bad. A defective TXV may result in a number of symptoms, including warm air instead of cool air coming out of vents, ice or frost forming on the evaporator coil, short-cycling (the unit turns on and off rapidly or runs continuously without stopping), and an unexplained increase in cooling costs.Additionally, the expansion valve can become clogged or defective. This issue causes the temperature and pressure of the refrigerant to be affected as it moves into the evaporator. There’s also the chance that the AC pressure switch has gone bad. This vital air conditioning part is responsible for regulating refrigerant flow through the ...

Re fertilizer ark.

Sam o'nella face reveal.

The primary method of charging a system changes based on the type of metering device. A piston system uses the superheat method of charging, and a TXV uses the subcooling method of charging. The illustration below shows how to add charge to a TXV system using probes. Monitoring temperature and pressure is critical to setting a proper charge. Sep 10, 2020 · 5. Outdoor Temperature Is Too Low. Similar to how the coils freeze when there is restricted airflow, they can also freeze if the temperature of the air your system is trying to cool is too low. Since the coils work by absorbing heat from the air, the lack of such heat can lead to condensation on the coils freezing over. 6. Aug 20, 2018 · There are many reasons why an expansion valve may suddenly go bad. Sometimes the parts are just defective. Other times clogging in the system will damage the part. In many cases, the part simply deteriorates due to age. Regardless of the cause, fixing a broken expansion valve can be challenging and should only be undertaken by a professional. Once you have ensured all the above things, you can adjust the thermostatic expansion valve (TXV). Step 1. With the help of a wrench and the backing wrench with the adjustable screw, the technicians are challenged to remove the hex cap located on the base of the TXV valve. Step 2. To increase the superheat, technicians are allowed to turn it ...How an A/C Expansion Valve Works. Bad Car A/C Expansion Valve Symptoms. 1) Warm Air From Vents. 2) Frost on the Vents. 3) A/C Compressor Always On. 4) Inconsistent Airflow. 5) A/C System Failure. A/C Expansion Valve Replacement Cost. What should suction pressure be on 410a, keeping this in mind?“For example, in an R-22 system, suction and head pressures would be 83 and 257 psia, while in an R-410A system, they would be 133 and 406 psia.”Additionally, what causes high pressure on an AC system? ... Will a bad Txv result in low suction pressure? When a TXV is restricted ...Symptoms of a bad motherboard and processor include a computer that does not boot at all or a computer that starts to boot and then stops. A computer that freezes is another sign that a motherboard and processor are bad.Jun 24, 2011 · Forum Rules. I have a 3Ton Carrier Heat Pump unit using 410A that has extremely high suction pressure around 250PSI. I also have a low liquid line pressure around 300PSI and my sub-cooling is around 40-50 Degrees. I have checked for a stuck liquid line solenoid but this system does not have one, and I checked the reversing valve and its ... Another common reason for overcharging a system, causing AC high-side pressure too high, is too much refrigerant(R134a, R410A). Additionally, there may be too much oil in the system. ... and potential system shutdown are the main symptoms of bad TXV. To conclude, that was all you needed to know when you face AC high side …110-120° F. What are the symptoms of an air conditioning system that has a bad compressor discharge valve: low discharge pressure, high suction pressure, and low amp draw. What is the purpose of an EPR valve: It increases pressure in a high-temperature evaporator coil when it is used on a dual-evaporator system.It is important that you check for temperature drop across any filter/driers or screens BEFORE reaching that “bad TXV” diagnosis. Be sure the evaporator and condenser coils are clean. This is just good …There are a number of ways to tell if your brake rotors are bad. If you suspect that they are bad, you should have them checked out by a mechanic. He will be able to tell you if they need replacing or not. You should always make sure your b... ….

Sometimes, it's good to be bad! We'd never suggest doing anything TRULY evil, of course, but sometimes relaxing your standards and letting go of the pressure to be perfect can be the absolute right thing to do. Share your own &quo...As the thermostatic expansion valve regulates the rate at which liquid refrigerant flows into the evaporator, it maintains a proper supply of refrigerant by matching this flow rate against how quickly the refrigerant evaporates (boils off) in the evaporator coil. To do this, the TXV responds to two variables: the temperature of the refrigerant ...TXV KNOWLEDGEIn cooling operation a bad Thermostatic expansion Valve could cause the suction pressure to drop to 0 PSIG It could cause the head pressure to r...In this HVAC training video, I will describe how I diagnose a bad TXV. A thermostatic expansion valve meters the flow of refrigerant into the evaporator coi...In this HVAC Video, I show how to tell if you have a liquid line restriction such as a clogged metering device, clogged filter drier, or clogged strainer scr...Rheem R-410A Heat Pump Troubleshooting. SYMPTOM POSSIBLE CAUSE REMEDY; Unit will not run ... • Bad TXV • Replace TXV. • Bad compressor • Replace compressor. Low vapor, cool compressor, iced indoor coil • Low indoor airflow • Increase speed of blower or reduce restriction. Replace air filter. ... SYMPTOMS POSSIBLE CAUSE CHECK OR …153 Post Likes 410A TXV Troubleshooting I am a fairly new tech so bare with me, went to a service call earlier today for no cooling on a 410a system. Air filters were clean, so went upstairs in the attic to find that the TXV was frozen over and the indoor coil was frost over some. The Blower was running great as it was passing thru the coil.Decomposition products formed from these reactions cause symptoms such as plugged cap tubes, sticking thermostatic expansion valves and abnormal compressor wear. ... Bad TXV Reply RonBurgandy619 ... I just did one 410a last week. pressures are 126psi-46.2f low side/ 418.9 psi - 93.9f high side vapor saturation 43f luiquid saturation 119f super heat …Definition of High Superheat. High superheat occurs when the temperature of the vapor in a refrigeration system is significantly higher than its saturation temperature. This can be caused by various factors, including improper refrigerant charge, low airflow across the evaporator coil, or a malfunctioning expansion valve. Symptoms of bad txv 410a, Below are some general installation concerns and tips to follow when installing a TXV: • Always follow the manufacturer’s installation guidelines. They take precedence over any of these general recommendations. • For suction lines less than 7/8 inch, place the sensing bulb at the 12 o'clock position on the suction line leaving the ..., Sep 18, 2020 · The main reasons your compressor will have simultaneously low head pressure and high suction pressure is due to: Bad or leaky compressor valves. Worn compressor piston rings. Leaky oil separator return line. Your compressor valves may become inefficient due to poor sealing from dirt and debris deposits. , Step 1: Locate the orifice tube. The orifice tube will be inside the high-pressure line to the evaporator. Most orifice tube systems have the evaporator under the hood or cowl, Find where the line steps up in size just before a joint. The orifice tube should be in there. Step 2: Open the line., R410A TXVs have been failing since spring on systems that are about 1 year or less in age. Failed TXVs on systems 1.5 to 3 tons although also possibly on larger but is being researched. This is not on being seen 100% across the board. Random even on units set side by side at the same time. Symptoms-- less than 1 year old. 410A Txv. , High superheat occurs when the temperature of the vapor in a refrigeration system is significantly higher than its saturation temperature. This can be caused by various factors, including improper refrigerant charge, low airflow across the evaporator coil, or a malfunctioning expansion valve. When superheat is too high, it can negatively impact ..., 2. Common Symptoms of a Faulty TXV in HVAC Systems. High or low suction pressure. Low superheat or high subcooling. Compressor overheating or short cycling. Uneven cooling or heating. Ice ..., TXV KNOWLEDGEIn cooling operation a bad Thermostatic expansion Valve could cause the suction pressure to drop to 0 PSIG It could cause the head pressure to r..., R-410A refrigerant took over R-22, which was banned in 2010 and phased out in 2015. R-32 is an even more efficient refrigerant for your HVAC system. R-410A is chlorine-free but still releases enough chemicals to have a high global warming potential. It costs between $3,200 to $6,800 on average to install an R-410A HVAC system., 153 Post Likes 410A TXV Troubleshooting I am a fairly new tech so bare with me, went to a service call earlier today for no cooling on a 410a system. Air filters were …, A symptom of a clogged liquid line filter drier is a temperature drop across the filter drier. Filter driers are typically shaped like a hot dog and are about the same diameter. If one end of the filter drier is a markedly higher or lower temperature than the other end, it is likely that the liquid line filter drier is clogged and may need to ..., Make sure it's installed properly and watch the pressures. If you replace one flush the liquid line. If the same problem exists with the new txv then your installers or someone who worked on it may have done something that contaminated the refrigerant. Reply. 06-30-2012, 09:40 AM #4., Mar 9, 2020 · This small amount of heat to reject will cause a low condensing pressure and temperature. Most of the refrigerant will then be stored in the condenser and receiver, simulating a pumped-down refrigeration system. Symptoms of a liquid line restriction include: Low evaporator (suction) pressure; High superheats; , There are many reasons why an expansion valve may suddenly go bad. Sometimes the parts are just defective. Other times clogging in the system will damage the part. In many cases, the part simply deteriorates due to age. Regardless of the cause, fixing a broken expansion valve can be challenging and should only be undertaken by a professional., Jan 9, 2017 · This will cause the following symptoms: Low evaporator (suction) pressure; High evaporator and compressor superheats; Low compressor amp draw; Short-cycling on the low-pressure control; Somewhat high discharge temperature; Low condensing (head) pressure; , High superheat occurs when the temperature of the vapor in a refrigeration system is significantly higher than its saturation temperature. This can be caused by various factors, including improper refrigerant charge, low airflow across the evaporator coil, or a malfunctioning expansion valve. When superheat is too high, it can negatively impact ... , A properly functioning A/C expansion valve is crucial for cold air, but this valve can fail without warning. Overlooking expansion valve problems allows refrigerant leaks, pressure issues, and corrosion to sneak in, escalating costs. Learn how to recognize symptoms of a bad A/C expansion valve early on to save you time and money down the road., In this HVAC Video, I show how to tell if you have a liquid line restriction such as a clogged metering device, clogged filter drier, or clogged strainer scr..., And R410A is the most common substitute for central air conditioning and heating split systems – an outdoor AC or heat pump and an indoor furnace or air handler. R410A is a hydro-flurocarbon (HFC) and is safe for the ozone layer. ODP = Zero. Puron is a brand of R410A developed by Carrier, and for some, the name is synonymous with R410A., This article explores how evaporators can become oil logged, and includes symptoms with explanations of a system with an oil-logged evaporator. This refrigeration system incorporates HFC-134a as the refrigerant. It has a thermostatic expansion valve (TXV) for the metering device and a receiver at the condenser outlet., Liquid-line solenoid valves. It is common practice to select liquid solenoids for a pressure drop equivalent to a 1° change in saturation temperature. For R-22 at 100°F, this is about 3 psi. If the same criterion is used for 410A, that is a 1° loss in subcooling; the valve would be sized for about 4.75-psi pressure drop., Sep 10, 2020 · 5. Outdoor Temperature Is Too Low. Similar to how the coils freeze when there is restricted airflow, they can also freeze if the temperature of the air your system is trying to cool is too low. Since the coils work by absorbing heat from the air, the lack of such heat can lead to condensation on the coils freezing over. 6. , Jan 8, 2016 · 1. AC system performing worse than usual and blowing warm air. One of the first symptoms of a problem with the AC expansion valve or orifice tube is an underperforming AC system. The AC expansion valve and orifice tube work together to regulate the flow of the AC system. If either component fails or has an issue, it can disturb the performance ... , Apr 5, 2023 · The cost to replace an expansion valve ranges from $100 to $700 or $400 on average. The valve itself makes up a large portion of that cost. Expect to pay $100 to $300 for a new TXV, depending on the brand and exact type of valve needed. You’ll also need your HVAC tech to replace any refrigerant they remove while replacing the valve. , Step 1: Locate the orifice tube. The orifice tube will be inside the high-pressure line to the evaporator. Most orifice tube systems have the evaporator under the hood or cowl, Find where the line steps up in size just before a joint. The orifice tube should be in there. Step 2: Open the line., And R410A is the most common substitute for central air conditioning and heating split systems – an outdoor AC or heat pump and an indoor furnace or air handler. R410A is a hydro-flurocarbon (HFC) and is safe for the ozone layer. ODP = Zero. Puron is a brand of R410A developed by Carrier, and for some, the name is synonymous with R410A., The TXV contains a sensing bulb attached to the suction line, which constantly reads the temperature. The TXV regulates refrigerant flow by using a movable valve pin against spring pressure to precisely control the flow of liquid refrigerant let into the evaporator coil. See the picture below of a TXV valve. The fourth component is the …, Mar 1, 2017 · TXV troubleshooting tips. TXV troubleshooting tips. Wednesday, March 1, 2017 Be social | Take part Keep me updated. Markets we serve; Automotive ... , A thermostatic expansion valve, commonly referred to as a TXV or TEV, is a flow control device used in refrigeration and air conditioning systems. The primary function of a TXV is to regulate the flow of refrigerant entering the evaporator coil in response to the cooling load, ensuring optimal performance and energy efficiency., Aug 13, 2023 · The expansion valve can prevent proper cooling of the cabin when it fails. What Does an Expansion Valve Do? To understand the role of the expansion valve, it helps first to have some knowledge of how the A/C system works. All automotive A/C systems use refrigerant as a heat transfer mechanism to remove heat from the cabin. , Restriction In The TXV Tube. The evaporator, compressor, and condenser will be starved of refrigerant if TXV is limited. Low amp draws, low head pressures, high superheats, and low suction pressures will result from this. Additionally, a refrigerant undercharged system exhibits many of the same symptoms as a system with a limited TXV system., It is stamped 4lbs 15oz. for the manufactures charge of 410A. 4. Last check by the tech from the company that installed it before going out of warranty was High side 275 psi, high side temp 70F, Low side psi was 115 Low side temp 50. This calculates to Super Heat of 12 more or less., Jan 25, 2016 · TXV FUNCTIONALITY: 1+2: The thermostatic expansion valve (TXV) sensing bulb senses the temperature at the evaporator outlet. Based on that temperature, pressure in the sensing bulb increases or decreases. 3: The increased or decreased pressure is transmitted through the capillary tube to the top half of the power element. 4: In the power element, the pressure from the bulb is exerted on the ... , Thermostatic expansion valves (TXV) are responsible for metering the proper amount of refrigerant into an evaporator coil. When they fail, they either cause the evaporator to be flooded (overfed) or starved (underfed) for refrigerant. This can be observed by measuring the superheat value of the refrigerant as it leaves the evaporator.