You’re dealing with a Lennox heat pump model SL22KLV, and error code 124 is flashing, indicating insufficient heating due to a stuck reversing valve. This valve changes the direction of refrigerant flow between heating and cooling modes.
A stuck valve prevents the system from switching to heating mode, causing the issue. You’ll need to troubleshoot the reversing valve, checking voltage, electrical connections, and pressure differences. Learn how to diagnose and resolve the issue to get your heat pump running smoothly.
Important Point
Understanding Error Code 124
When your Lennox heat pump model SL22KLV displays error code 124, it’s telling you there’s a problem that needs attention.
Specifically, it’s signaling an insufficient heating issue related to the reversing valve. This valve is responsible for changing the direction of refrigerant flow between heating and cooling modes.
A stuck valve can cause the system to malfunction, leading to insufficient heating. The reversing valve’s slide can get stuck due to mechanical or electronic failure, often caused by overheating or contamination from a burned-out compressor.
You’ll need to diagnose the issue by checking the solenoid’s voltage supply in both heating and cooling modes.
Also, Read: Lennox SL22KLV Heat Pump Error Code 123: Insufficient Cooling Due to Evaporator Issues
Troubleshooting the Reversing Valve
When troubleshooting the Lennox Heat Pump Model SL22KLV, you’ll want to identify symptoms of a stuck reversing valve, such as the system malfunctioning or failing to switch between modes.
To diagnose the issue, you’ll need to check if the valve is receiving 24 volts and if the slide is stuck due to overheating or contaminants.
Reversing Valve Diagnosis
As you proceed with diagnosing the Lennox Heat Pump Model SL22KLV error code, the reversing valve warrants close attention.
This component plays a vital role in the A/C and HVAC system’s heat transfer process. During diagnosis, you’ll need to inspect the valve’s electrical connections to the control board.
Verify that the valve’s solenoid coil isn’t damaged, and check for any signs of physical damage or wear.
If you suspect an issue with the reversing valve, a thorough examination is necessary to isolate the problem.
A faulty reversing valve can trigger error code 124, indicating insufficient heating.
Reversing Valve Symptoms
Since you’re now inspecting the reversing valve symptoms, vital to recognize telltale signs of valve malfunctions.
If the reversing valve seems stuck in heating mode, check that 24 volts is being applied to the solenoid; if it is, the valve is bad.
Similarly, if it’s stuck in cooling mode, verify 24 volts is being applied to the solenoid; if it is, the valve thinks it’s supposed to be in cooling mode and won’t switch to heating mode.
A stuck valve can cause system malfunctions; lightly tapping on the valve body or switching between cooling and heating modes can free it.
If the valve is stuck in the middle, the slider is stuck or leaking high-side refrigerant to the low side, causing the compressor to run hot and increasing the amp draw.
Also, Read: Lennox SL22KLV Heat Pump Error Code 122: High Pressure Switch Open Detected
Voltage and Pressure Requirements
When checking the voltage and pressure requirements for the Lennox Heat Pump Model SL22KLV, you’ll need to verify the reversing valve has a minimum of 24 volts to energize the solenoid.
This solenoid requires a specific pressure differential of 30-70 psi between the high and low sides for the slider to move and switch modes.
You’ll need to check for continuity and magnetic pull in the reversing valve solenoid coil to certify proper operation.
Reversing Valve Voltage
You must guarantee the reversing valve receives 24 volts from the defrost board to energize the solenoid and change the direction of refrigerant flow. This voltage is vital for the solenoid coil to function properly. A malfunction in the reversing valve can lead to insufficient heating, causing the system to malfunction.
| Voltage Requirement | Solenoid Coil Function | Reversing Valve Operation |
|---|---|---|
| 24V | Energizes solenoid coil | Changes refrigerant flow direction |
| Low voltage | Weakens solenoid | Fails to switch modes |
| No voltage | De-energizes solenoid coil | Stuck in one mode |
When troubleshooting, check voltage, pressure, and temperature readings to identify the cause of the malfunction. Mechanical or electronic failure can cause the valve to stick, resulting in inadequate heating.
Reversing Valve Pressure
The pressure differential between the high side and low side plays a critical role in reversing valve operation.
You need a 70 psi pressure differential for the slider to move. Without it, the system won’t switch modes, causing the compressor to run hot, increasing amp draw, and tripping the internal overload protection switch.
In this scenario, suction line pressures will be higher than normal, while high side pressures will be lower, making it seem like the compressor is bad.
Temperature differences between the suction and discharge lines can indicate a problem with the reversing valve, with temperature differences of 4 degrees or lower expected in normal operation.
Also, Read: Lennox SL22KLV Heat Pump Error Code 121: Low Pressure Switch Open Detected
Temperature Readings and Pressure Checks
As you diagnose the Lennox Heat Pump Model SL22KLV, accurate temperature readings and pressure checks become crucial.
Take temperature readings of the suction line entering and leaving the reversing valve, recording them approximately 6 inches away from the body.
In cooling mode, take readings at the discharge line and the line going to the outdoor coil, and another set at the constant suction line and the line going to the indoor coil.
Certify temperature differences are 4 degrees or lower, except in extremely high outdoor temperatures.
Check the solenoid coil for continuity and magnetic pull to certify it’s functioning properly, and verify a 30-70 psi pressure differential.
Diagnosing the Reversing Valve
Now that temperature readings and pressure checks are complete, focus shifts to the reversing valve, a critical component that changes the direction of refrigerant flow.
This valve defaults to heating mode in 90% of systems, and its malfunctioning can cause the system.
To diagnose a stuck valve, follow these steps:
- Verify solenoid operation: Certify 24 volts are being applied to the solenoid coil, which moves the pilot valve, creating a pressure differential.
- Check pressure differential: Confirm a 30-70 psi pressure differential is present to push the slide laterally.
- Monitor temperature differences: Check suction line temperature readings entering and leaving the reversing valve, expecting differences of 4 degrees or lower in normal operation.
- Identify stuck valve symptoms: Look for signs of a stuck valve, including mechanical or electronic failure, or failure to switch modes.
Also, Read: Lennox SL22KLV Heat Pump Error Code 120: Thermistor Failure Detected
Review and Troubleshooting Summary
You’ve reached the review and troubleshooting summary stage, where all previous diagnostic steps converge to identify the root cause of the Lennox Heat Pump Model SL22KLV error code 124.
By now, you’ve diagnosed the reversing valve, checking voltage, pressure, and temperature readings.
You know that temperature differences between the suction and discharge lines indicate a problem.
The reversing valve requires a specific pressure differential of 30-70 psi to switch modes.
If the valve is stuck, the system will malfunction, and if it’s stuck in cooling mode, confirm 24 volts are getting to the solenoid.
You’ve ruled out the control board as the culprit if it’s providing proper voltage to the solenoid.
Now, it’s time to review your findings to pinpoint the root cause of the insufficient heating issue.
Resolving the Insufficient Heating Issue
When insufficient heating persists, vital to identify the root cause, which often lies with the reversing valve.
As a Lennox SL22KLV heat pump model owner, you should know that resolving the insufficient heating issue requires attention to detail.
- Guarantee the safety float is clear of water and connections to the power source are secure to prevent error code E124.
- Verify the reversing valve has a 30-70 psi pressure differential to switch modes; otherwise, it won’t, leading to insufficient heating.
- Diagnose a stuck reversing valve by checking 24 volts applied to the solenoid coil’s continuity and magnetic pull.
- Monitor temperature differences between suction and discharge lines; 4 degrees or lower is normal, except in extremely high outdoor temperatures.
Also, Read: Lennox SL22KLV Heat Pump Error Code 119: Outdoor Airflow Restriction Detected (Blocked Coil/Fan)
Frequently Asked Questions
What Is Error Code 124 on a Lennox Thermostat?
You’re dealing with error code 124, which signals heat pump issues, thermostat problems, or faulty sensors, leading to heating malfunctions, system failures, causing temperature fluctuations, compressor issues, outdoor unit errors, or defrost mode problems, requiring diagnostic challenges to resolve.
How Do You Unstick a Reversing Valve on a Heat Pump?
You’re stuck with a faulty reversing valve, a million things running through your mind! To unstick it, try cleaning and lubricating the valve stuck troubleshooting process, followed by heat pump diagnosis, and thorough valve malfunction diagnosis for a smooth fix.
What Is Error Code E124?
You’re dealing with a frustrating issue: error code E124. This code typically indicates a thermostat fault, faulty operation, or technical glitch, often caused by valve problems, heating faults, or system malfunctions, which require code explanations and troubleshooting to resolve.
What Are the Symptoms of a Bad Reversing Valve for a Heat Pump?
Are you experiencing inconsistent heat pump performance? You might be dealing with a faulty reversing valve, causing symptoms like valve stuck open, heat pump inefficiency, leaks, faulty operation, noise issues, ice buildup, electrical faults, mechanical failure, or corrosion problems.
Conclusion
You’ve reached the end of the troubleshooting tunnel, and now it’s time to turn up the heat on your Lennox SL22KLV model. Error code 124 was just a roadblock, but you’ve navigated through voltage and pressure checks, temperature readings, and pressure tests.
Diagnosing the issue was like finding the missing piece of a puzzle – it’s now clear as day. Resolving the insufficient heating issue is within your grasp; tighten the last screws, and your system will be purring like a well-oiled machine.
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