THE PROBLEM. The expansion valve is an advanced and fragile device. As it operates under high pressures and is temperature sensitive,
improper working conditions as well as impurities inside the loop
can cause it to malfunction. If the expansion valve is stuck open or clogged, the A/C system will not cool properly.
What are the symptoms of a stuck expansion valve?
When stuck closed,
a higher than normal high side reading will be seen
. Typically, this will be over 400 psi and climb until the high-pressure switch shuts down the system. Very low or very high readings on the high-side gauge indicate a faulty expansion valve.
How do you unstick an expansion valve?
How do you unstick a Txv? Even holding he bulb in your hand should provide enough heat to open the valve. Next,
place the TXV bulb into cold water
. This should cause the expansion valve to close reducing the amount of refrigerant to pass thought the TXV into the coil.
What controls the expansion valve?
Thermostatic Expansion Valve uses a valve mechanism to control the flow of liquid refrigerant into the evaporator coil. The flow is controlled by
the pressure in the evaporator
. This type of metering device is able to operate well when the load fluctuates and hence is suitable for use in air conditioning system.
How do you test an expansion valve?
- Make sure the AC unit is plugged in or, if it is in an automobile, turn the vehicle on. …
- Use the manual to locate the thermostatic expansion valve. …
- Lift the sensing bulb from the suction bulb well. …
- Hold the sensing bulb in your hands for two minutes or place it in warm water.
What happens if expansion valve goes bad?
If the AC expansion valve fails or sticks open,
it will cause the compressor to pump refrigerant through the vehicle’s AC system
, even when it may be undesirable for it to do so. This will put an additional strain on the compressor and associated AC components, making them more susceptible to premature failure.
How long do expansion valves last?
There isn’t a specific lifespan of the valve
, it’s more just a wear and tear kind of situation. Obviously the more you use the air conditioning, the quicker it will wear down. Here’s a look at some of the signs you can watch for that can signal the end of your expansion valve’s lifespan.
What does a bad expansion valve look like?
The most recognizable symptom of a bad A/C expansion valve is when you turn on your air conditioner and
warm air starts blowing out of the vents
. This would obviously mean that not enough refrigerant is making its way to the core of the evaporator.
How do you adjust an expansion valve?
The TXV cannot be adjusted open or closed, it is a modulating valve. Turning the adjustment stem clockwise will only increase spring pressure causing a higher superheat. Turning the adjustment stem
counterclockwise
will decrease spring pressure reducing superheat.
What are the 4 types of expansion valve?
- Thermal Expansion Valves (TEVs)
- Manual Valves.
- Capillary Tubes.
- Automatic Valves.
- Electronic Expansion Valves.
- Float Valves.
Why is automatic expansion valve not used?
When the load on the evaporator is
high it won’t allow more flow of the refrigerant as
per the requirement. … Thus the automatic expansion valve does not allow the control of the flow of the refrigerant through it which is very important for the efficient operation of the refrigeration plant.
Can an expansion valve be cleaned?
Can you clean an AC expansion valve?
Pretty much anything can be cleaned
. But if the new part costs so little, it would not be worth the effort or risk if it was not cleaned properly.
What does an expansion valve do on an AC unit?
A thermostatic expansion valve (TXV) (see Figure 1) is a
refrigeration and air conditioning throttling device that controls the amount of refrigerant liquid injected into a system’s evaporator
—based on the evaporator outlet temperature and pressure—called the superheat.
How much does it cost to replace an expansion valve?
But on average, car owners pay somewhere
between $240 and $330
in most cases to do AC expansion valve replacement. That includes parts, which will run you right around $100, and labor, which will cost about twice that.
How do you diagnose a bad TXV valve?
Check the subcooling, superheat and pressures again. If there’s no change, that’s a further indication of a TXV problem. Another test is to
put the sensing bulb in ice water and checking the pressures superheat
, and subcooling again. If they don’t change, it’s a bad TXV.
What happens if expansion valve is stuck open?
If the expansion valve is stuck open or clogged,
the AC system won’t cool properly
. A clogged valve leads to insufficient refrigerant, increasing the pressure in the system and causing the AC compressor to overheat.
