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James A/C Co.
serving Do-It-Yourselfers since 1990.
Satisfying every customer....one at a time!
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Call toll free 1-866-584-0355 or 1-903-759-2160 309 Patriot Circle, Longview, TX 75604-2240


THE THERMOSTATIC EXPANSION VALVE (TXV)
The thermostatic expansion device is an orifice for the refrigerant flow. It is a very sophisticated orifice, though. It senses the pressure of the refrigerant coming into the evaporator as well as the temperature of the refrigerant as it leaves the evaporator and then meters the flow of refrigerant into the evaporator to keep it almost perfectly within the engineered specification.
| All flow control devices are under pressure from the refrigerant and are part of the "sealed system". Never cut into these tubes or lines or unscrew joints with the pressure still in the system. |
Before thinking that this expansion valve is your problem, be sure the evaporator coil is clean and the blower is on the right speed and that there is no obstructions of the air flow. If any of these exist incorrectly, the thermostatic expansion valve will appear to not be working well.
Other types of devices that will more likely be in your system as the flow control device rather than this expansion valve are:
- PISTON/ORIFICE:
- This may be nothing but an orifice or it may be an orifice and a floating piston device.
If you suspect problems from this device you can clean it out or if replacement is necessary, then you will have to obtain a new one from a dealer. Seek his advice here. He will likely be willing to give free advice.
- CAPILLARY TUBE(S):
- This tube(s) is very small and will be of specific lengths to control the flow of refrigerant. It acts as nothing but a restriction to the flow of refrigerant and is controlled by the pressure of the refrigerant from within the line coming from the condenser coil. The capillary tube(s) will flow less if they are longer and more if they are shorter. When they become coated with gums or carbon on the inside and thus restrict too much, it is usually at the inlet end. A short section of the tube(s) may be cut out of the system and solve the problem.
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comments or suggestions, please email me at James' A/C Co.
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