If the pressure does not change, the conclusion must be drawn that the TXV is faulty and a probable cause is that the sensor lamp has lost refrigerant. TXV is now measuring more refrigerant in the evaporator, but the valve continues to pump at the same rate.
Low evaporation of the refrigerant leads to lower pressures. High superheat - High superheat is also caused by the evaporator and compressor reducing hunger for refrigerant. Since the TXV is limited, the vaporizer becomes inactive and overheats. This leads to overheating of the compressor.
The average cost to replace an air conditioning expansion valve is between 240 and 336. Labor costs are estimated to be between 170 and 215, while parts cost between 70 and 121.
Check the evaporator coil and remove the TXV sensor lamp from the suction line. Check the subcooling, superheat and pressure again. Another test is to put the sensor bulb in ice water and check the heating and subcooling pressures again. If they don’t change, it’s a bad TXV.
A thermal expansion valve or thermostatic expansion valve (often abbreviated as TEV, TXV or TX valve) is a component of refrigeration and air conditioning systems that regulates the amount of refrigerant released into the evaporator and therefore the superheat, i.e. the difference between the current coolant
If there is no pressure change, the conclusion is that the TXV is faulty and a probable cause is that the bulb has lost a reservoir of coolant. TXV is now measuring more refrigerant in the evaporator, but the valve continues to pump at the same rate.
When a TXV is limited, the evaporator, compressor and condenser will run out of refrigerant. This causes low suction pressure, high superheat, low amperage, and low compression pressure. The reservoir can also overfill if too much coolant is added.
Testing an AC Controller
Defective thermal expansion valve
Temperature drop in the filter drier
A: A TXV can be too open or too closed. An opening that is too large is also referred to as a charged and means that the boiling refrigerant has penetrated too much into the evaporator coil, which is evident as a slight overheating.
The thermal expansion valve connects to the smaller copper tube that connects to the air conditioner inside or outside the air conditioner. It is located just in front of the evaporator coil to control the amount of refrigerant flowing through the evaporator.
The right model for your system
In these cases it is much cheaper for the customer to replace the valve than to clean it. It is very difficult to tell if a thermostatic expansion valve is clean. Dirt or contamination of the TXV can prevent proper flow of lubricating oil through the system and back to the compressor.
The thermal expansion valve (TXV) is installed to control the refrigerant flow to the evaporator based on the refrigerant load. TXV measures superheat at the outlet and responds by increasing or decreasing the amount of refrigerant flowing through the evaporator to try to maintain a constant superheat.
It is now extremely important for the HVAC technician to understand the design and operation of this valve. The Thermostatic Expansion Valve (TXV) is a precision unit designed to control the rate at which liquid refrigerant flows through the evaporator.
I highly recommend replacing the controller. If the coupling is defective, the controller does not need to be replaced. If that was the bearing, the expansion valve may not need to be replaced depending on whether or not metal chips have been introduced into the cooling system.
When the valve is fully mechanically bolted (no welding) it takes approximately 15 minutes plus pumping, pressure testing, vacuum and charging. I replaced at least a hundred regulators and never had to pull the reel.