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To unstick a reversing valve on a heat pump: 1) Power off the unit. 2) Tap gently on the valve body with a rubber mallet to dislodge any debris; avoid using metal hammers that can damage the valve. 3) Apply heat with a hair dryer or heat gun to the valve solenoid to expand the metal slightly, facilitating movement. 4) Manually activate the solenoid by applying 24V directly to it (check the wiring diagram for correct terminals)
Potential challenges/issues and probable solutions while unsticking a reversing valve
| Challenge/Issue | Symptom | Diagnostic Method | Solution | Tools/Supplies Needed |
|---|---|---|---|---|
| Valve Stuck in Heating or Cooling Mode | The Heat pump fails to switch modes | Listen for the clicking sound of the valve shifting when changing modes on the thermostat. Use a multimeter to check for proper voltage at the solenoid. | 1. Manually tap the valve with a rubber mallet to free it. 2. Apply electrical heat (with a heat gun) to the valve body to expand it slightly and attempt to switch modes again. | Rubber mallet, multimeter, heat gun |
| Solenoid Failure | No clicking sound when changing modes | Use a multimeter to check for continuity across the solenoid coil. A lack of continuity indicates a failed solenoid. | Replace the solenoid coil. Ensure the power to the unit is off before starting the replacement. | Multimeter, replacement solenoid, screwdrivers, safety gloves |
| Low Refrigerant Charge | Poor heating or cooling performance; The valve may not shift due to insufficient pressure differential | Attach gauges and measure the pressure on both the high and low sides of the system. Compare readings to manufacturer specifications. | Locate and repair leaks. Recharge the system with the correct type and amount of refrigerant according to the manufacturer’s specifications. | HVAC gauges, refrigerant, leak detector (soap solution or electronic), safety goggles, gloves |
| Electrical Issues (Wiring or Thermostat) | The Valve does not receive the signal to switch modes | Inspect wiring for signs of damage, loose connections, or corrosion. Use a multimeter to verify the signal from the thermostat to the valve. | Repair or replace damaged wires or connectors. If the thermostat is faulty, replace it according to the manufacturer’s guidelines. | Multimeter, wire strippers, crimpers, replacement wires/connectors, replacement thermostat (if necessary) |
| Mechanical Obstruction | The valve is physically obstructed from moving | Inspect the valve for any visible signs of debris or obstruction. Carefully disassemble parts accessible without releasing refrigerant. | Clean the valve and surrounding area with a non-corrosive cleaner. Reassemble and test. For internal obstructions, professional assistance may be required. | Screwdrivers, cleaning solvent, soft-bristle brush, safety glasses, gloves |
In this blog, we will talk about how to unstick a reversing valve and its troubleshooting tips in detail.
Check if the Valve is Stuck
The valve uses a 24VDC solenoid with copper windings that pull the internal plunger to slide the internal chambers of the valve into place for heating or cooling.
Tools:
- Refrigerant gauges.
- Multimeter.
Steps:
- Connect refrigerant gauges and take suction and discharge pressures. They should vary significantly from heating to cooling mode. If there’s no variation, the blockage is inside of it.
- Use a digital multimeter to check solenoid coil resistance by reading across the terminals of its wiring connections. It should be between 24-28 ohms. Anything higher means copper windings are burned out.
This process will let you know whether or not your valve is bad.
Image Credits: Heat Pump Installation by Phyxter.ai is licensed under (CC BY 2.0)
Replace Failed Solenoid
If the solenoid fails the test, replace it:
Tools:
- Socket set.
- Wire cutters.
- Multimeter.
- Replacement solenoid (24VDC, SPST, 9W maximum).
Steps:
- Switch off the unit at the breaker panel/disconnect switch.
- Disconnect wires connected to the faulty solenoids and label them accordingly.
- Remove the faulty solenoid while you note the orientation of its internal plunger mechanism.
- Install replacement making sure to engage it correctly into the valve shift lever.
- Reconnect all wires securely without pinching or straining connection points with excessive tension.
- Power the unit back on and listen for an audible click when the solenoid activates for verification purposes before proceeding further.
Use Temperature Extremes
If the solenoid tests fine but the valve sticks in either position, apply heat/cool cycles:
Tools/Materials:
Plastic mallet
Steps:
- Set the system to full heat mode (over 100°F target temp).
- Allow at least 15 minutes for the suction line entering the valve to exceed 90°F.
- Tap gently on the valve body with the plastic mallet to resonate the vibration of stuck internals while warmed up.
- Repeat the process in full cool (below 50°F target) to cold shock internals too.
- Avoid forcefully hitting the valve so hard that it cracks the internal brass/stainless chambers. The heat/cool cycles combined with gentle tapping resonate can free stuck components internally in many cases.
Replace Entire Valve
If unable to unstick, replace the entire reversing valve as necessary:
Tools/Materials:
- Tubing cutter
- Braze torch kit
- Nitrogen tank
- P51 refrigerant recovery machine
- 3-4 Ton bi-directional 410A TXV replacement valve
- 410A refrigerant scale
Steps Overview:
- Reclaim refrigerant charge from the unit using the recovery machine.
- Cut out the failed valve with the tubing cutter.
- Braze install new proper size valve.
- Pressure test system for leaks above 300 PSI with nitrogen.
- Vacuum system below 500 microns.
- Recharge precise factory spec amount of R410A refrigerant and no more or less than what it specifies.
- Test operation in both heating and cooling modes to confirm good reversing action.
Reference: Reversing valve
Hello…I am Manjula Sivapuri. I have completed my graduation in Chemistry. Currently working as a Chemistry Subject Matter expert in LambdaGeeks. My keen interest in chemistry has brought me to this platform to share my knowledge on the subject. I hope my work will make you understand the topics well.
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