Publish Time: 2025-03-21 Origin: Site
Four-way valves, also known as reversing valves, are key components of heat pumps that allow the system to switch between heating and cooling modes. It works by reversing the flow of refrigerant through the system. Here's a detailed explanation of how it works:
In a heat pump, four-way valves change the direction of refrigerant flow, allowing the system to:
Heating the interior space (by absorbing heat from the outside and releasing it into the interior).
Cool the interior space (by absorbing heat from the interior and releasing it to the outside).
Valve body: Contains an internal channel to direct refrigerant flow.
Slider or piston: Moves inside the body to change the flow path.
Electromagnetic coil: The electromagnetic coil that controls the movement of the slider or piston.
Refrigerant port: Four ports for connecting the compressor, indoor coil, outdoor coil, and suction pipe.
Cooling mode
The electromagnetic coil is powered off (no power).
The slide or piston in the valve moves to the default position.
The refrigerant flow is as follows:
Compressor exhaust → outdoor coil (condenser) → expansion device → indoor coil (evaporator) → compressor suction.
It absorbs heat from the indoor air and releases it to the outside, cooling the indoor space.
Heating mode
The electromagnetic coil is energized (powered by 24V AC from the thermostat).
The slide or piston in the valve moves to a new position.
Refrigerant reverse flow:
Compressor exhaust → indoor coil (condenser) → expansion device → outdoor coil (evaporator) → compressor suction.
Heat is absorbed from the outdoor air and released into the interior, heating the interior space.
Refrigerant reflux: The 4-way valve changes the flow path of the refrigerant, allowing the heat pump to switch between heating and cooling.
Solenoid control: The solenoid is controlled by a thermostat. When the thermostat requests a change in mode, it sends a signal to turn on or off the solenoid valve, thereby moving the valve.
Differential pressure: The movement of the slider or piston inside the valve is usually assisted by the differential pressure in the refrigerant line.
Cooling mode
Compressor → Outdoor coil (condenser) → expansion unit → indoor coil (evaporator) → compressor
Heating mode
Compressor → indoor coil (condenser) → expansion unit → outdoor coil (evaporator) → compressor
Stuck valve: Debris, sludge or mechanical wear can cause the valve to become stuck, preventing it from moving.
Solenoid valve coil fault: The solenoid valve coil is faulty, causing the valve to fail to switch positions.
Refrigerant problem: Low or unbalanced refrigerant level will affect the operation of the valve.
Check solenoid coils and wiring regularly for damage.
Refrigerant is correctly charged to avoid valve strain.
Clean the outdoor unit to prevent debris from entering the system.
By understanding how four-way valves work, you can better diagnose and troubleshoot problems in heat pump systems. If you experience ongoing problems, consult a licensed HVAC technician for professional help.
The reversing valve in a heat pump is a key component that controls the direction of refrigerant flow, allowing the system to switch between heating and cooling modes. Here's how to find it:
Position of reversing valve
1. Near the compressor: The reversing valve is usually located near the heat pump compressor, usually in the outdoor unit of the system.
2. Follow refrigerant lines: Look for brass or copper valves with multiple refrigerant lines (usually four) connected. It usually has an electromagnetic coil attached to one side.
3. Outdoor unit: In most residential heat pumps, the reversing valve is located inside the outdoor condenser unit. Open the access panel and locate it.
Identify directional valves
• It is usually cylindrical or rectangular.
• It has one large tube (from the compressor) and three small tubes (leading to the indoor coil, outdoor coil and suction tube).
• The solenoid (a small cylindrical assembly) is usually attached to the side of the valve.
Location prompt
• Refer to the heat pump instruction manual or schematic diagram for specific operation.
• If you are unsure, consult a licensed HVAC technician to avoid damaging your system.
To check and repair a four-way valve in a heat pump, follow these steps:
A four-way valve, also known as a reversing valve, is a key component of a heat pump that allows the system to switch between heating and cooling modes by reversing the flow of refrigerant. Usually located near the outdoor unit compressor, there are four refrigerant pipes connected to it
Multimeter (check electrical components)
Soft mallet or screw shank (for tapping valves)
Refrigerant pressure gauge
Screwdrivers and wrenches
Replacement parts (if necessary, such as electromagnetic coils or entire valves)
Step 1: Power off the system
Turn off the heat pump at the thermostat and disconnect the power at the circuit breaker to ensure safety.
Step 2: Check the solenoid
Locate the electromagnetic coil attached to the four-way valve. Check for obvious damage, loose connections, or burned wires.
Test coil continuity with a multimeter. If there is no continuity, the coil is faulty and needs to be replaced.
Step 3: Check the refrigerant pressure
Connect the refrigerant pressure gauge to the system to ensure that the refrigerant level is appropriate. Too low or unbalanced refrigerant will affect the work of the valve.
Step 4: Test valve operation
Power on the system and switch between heating and cooling modes. Listen for a clicking sound, which indicates that the valve is trying to shift.
If the valve does not move, tap your hand on the valve with a soft mallet or screwdriver to release any stuck internal parts.
Step 5: Verify the electronic signal
Use a multimeter to check that the solenoid is receiving the correct voltage from the control board. If no voltage is detected, the problem may be related to the control board or wiring.
If the valve is stuck and tapping does not solve the problem, the valve may need to be replaced.
If the solenoid coil is faulty, replace it with a compatible component.
For serious problems, such as internal damage or refrigerant leaks, the entire valve may need to be replaced. This is a complex task that should be performed by a licensed HVAC technician.
The following is a simplified diagram of the four-way valve and its components:
【 Compressor 】→【 Discharge pipe 】→【 four-way valve 】→【 Indoor coil (heating)/Outdoor coil (cooling) 】
Discharge line: Transfer high pressure refrigerant from compressor to valve.
Four-way valve: Guide refrigerant to indoor coil (heating) or outdoor coil (cooling).
Solenoid: Electrically controlled valve operation.
In the routine maintenance of HVAC, valves and electromagnetic coils should be checked regularly.
Ensure the refrigerant level is balanced to prevent valve strain.
Clean the outdoor unit to avoid debris buildup that may affect valve operation.
If you are unsure of any steps or lack the necessary tools, it is recommended to contact a professional HVAC technician for assistance.
Unstick the heat pump four-way valve, you can try the following steps:
1. System power cycle: Turn off the heat pump at the thermostat and circuit breaker. Wait about 5-10 minutes and then turn it back on. This can sometimes reset the system and release the reversing valve1
2. Tap the valve: Locate the directional valve (usually a brass component connected to multiple refrigerant lines). Gently tap the valve body with a soft mallet or the handle of a screwdriver. Be careful not to damage the valve or surrounding components. This can help remove any tiny debris or corrosion that causes the valve to stick
3. Check the electromagnetic coil: The reversing valve is controlled by the electromagnetic coil. Ensure the coil is working properly by checking for proper voltage and continuity. If the coil is faulty, it may need to be replaced
4. Check the refrigerant liquid level. If the refrigerant liquid level is too low or unbalanced, the working of the reversing valve will be affected. If the refrigerant is incorrectly charged, the valve may not shift properly. Ask technical personnel to check and adjust the refrigerant level.
5. Clean the valve: If debris or sludge causes the valve to jam, it may need to be thoroughly cleaned. This usually involves flushing the system with a cleaning solution, which should be done by a qualified HVAC technician to avoid damaging the system1.
6. Replace the valve: If the above steps do not solve the problem, the reversing valve may be permanently stuck or damaged. In this case, replacement is the only solution. This is a complex task that should be performed by a licensed HVAC professional
If the problem persists, or you are unsure whether to perform any of the above steps, it is recommended to contact a qualified HVAC technician for assistance.
When using a multimeter to check the heat pump four-way valve (reversing valve), perform the following steps. This process will help you diagnose whether the problem is electrical (electromagnetic coil) or mechanical (valve itself).
Multimeter (set to measure resistance/ohms and voltage)
Screwdrivers and wrenches
Soft mallet or screw shank (for tapping valves)
Safety gloves and goggles
Step 1: Turn off the power
Turn off the heat pump at the thermostat and disconnect the power at the circuit breaker to ensure safety.
Step 2: Locate the four-way valve
The four-way valve is usually located near the outdoor unit compressor. It has four refrigerant lines connected and an electromagnetic coil attached to one side.
Step 3: Check the solenoid
Visually inspect solenoid coils for damage, loose wires or burnt connections. If the coil looks damaged, it may need to be replaced.
Step 4: Test the continuity of the solenoid
Disconnect the wire from the solenoid coil.
Set the multimeter to measure resistance (ohms).
Place the multimeter probe on the terminal of the electromagnetic coil.
The resistance of a good solenoid is usually between 20 and 60 ohms.
If the multimeter reads OL (open circuit) or 0 ohms, the coil is faulty and needs to be replaced.
Step 5: Check the solenoid voltage
Reconnect the wires on the solenoid.
Turn on the power and set the thermostat to switch between heating and cooling modes.
Set the multimeter to measure AC voltage.
Place the multimeter probe on the solenoid terminal.
When the system requires mode switching (heating or cooling), you should read 24 volts AC.
If there is no voltage, the problem may be in the thermostat, control board, or wiring.
Step 6: Test valve operation
If the solenoid coil receives the correct voltage, but the valve does not move, tap the valve body with a soft mallet or the handle of a screwdriver. This can sometimes release a stuck valve.
If the valve still does not move, it may be mechanically stuck or damaged and needs to be replaced.
Replace the solenoid coil: If the solenoid coil fails, replace it with a compatible part.
Replace the valve: If the valve itself is stuck or damaged, the valve needs to be replaced. This is a complex task that includes refrigerant recovery, brazing and system charging. It is recommended to hire a licensed HVAC technician to do the job.
The expected reading of the test multimeter is incorrect
Solenoid continuity ohms (Ω) 20-60 ohms ol (open circuit) or 0 ohms
Solenoid voltage AC voltage (V~) The AC voltage during mold change is 24v 0v or no voltage
Check solenoid coils and wiring regularly for damage.
Ensure the refrigerant level is balanced to prevent valve strain.
Clean the outdoor unit to prevent debris accumulation.
If you are unsure of any steps or lack the necessary tools, it is recommended to contact a professional HVAC technician for assistance.