When your Lennox heat pump model SL22KLV displays error code – 106, it means the defrost sensor has failed, causing inefficient heating and ice buildup on the outdoor coil. You’ll notice a 2-3 degree temperature drop during defrost mode, and if auxiliary heat doesn’t kick in, the recovery process becomes uncomfortable.
You can troubleshoot this issue, but it’s vital to understand the root cause to prevent future failures.
Important Point
Understanding Defrost Mode Issues
When your Lennox heat pump goes into defrost mode, you can expect cold air to replace the warm air coming out of the registers, causing the house temperature to plummet from 20 degrees to a chilly 18-19 degrees.
This drop in temperature takes a substantial amount of time to recover, affecting the economy of your heat pump system.
During defrost mode, the heat pump system is supposed to switch to auxiliary heat, but if it doesn’t, the recovery process becomes uncomfortable.
The technician should verify the W1 terminal in the outdoor unit is connected to the aux heat kit in the air handler, allowing backup heat to activate during defrost mode.
Also, Read: Lennox SL22KLV Heat Pump Error Code 105: Low Pressure Detected in Outdoor Unit
Defrost Sensor Failure Diagnosis
Your heat pump’s defrost sensor is a crucial component that guarantees efficient heating.
To diagnose a faulty defrost sensor, you’ll need to test its functionality. Start by ensuring the defrost control board is working correctly by checking the voltage supply to the defrost sensor. Typically, the defrost control board provides 5-6 volts DC to the defrost sensor.
Next, test the defrost sensor by lowering its temperature to see if it closes. Then, heat the sensor to check if it opens. If the defrost sensor fails to close or open as expected, it’s likely faulty and should be replaced.
Symptoms of a faulty defrost sensor include ice buildup, constant or intermittent outdoor fan operation, and extended defrost times.
Troubleshooting Steps for Defrost Sensor Failure
You’ll need to check the power supply to guarantee the defrost sensor is receiving the correct voltage.
Next, test the defrost sensor operation by simulating temperature changes to verify it’s opening and closing as expected.
Finally, verify that the wiring connections between the defrost sensor and control board are intact.
Check Power Supply
The power supply is a critical component in the operation of your Lennox heat pump, and issues with it can trigger a defrost sensor failure error code.
You need to guarantee the power supply to the defrost sensor is stable and within the recommended specifications.
- Check the voltage supply to the defrost board, certifying it’s within the specified range (usually 24V AC).
- Verify that the defrost sensor power supply wires are securely connected to the defrost sensor and the board.
- Inspect the power supply wiring for signs of damage, corrosion, or wear.
- If you’re using an external power supply, guarantee it’s functioning correctly and providing a stable output.
Test Defrost Sensor
Faulty defrost sensor readings can stem from a malfunctioning sensor itself.
To test the defrost sensor, you’ll need to check the ambient temperature and the RETURN AIR temperature. When the pump goes into defrost mode, the defrost sensor should detect the temperature and trigger the defrosting process.
If the heat pump is experiencing ice buildup, it may be due to a faulty sensor. As a heat pump and air conditioning technician, you know that heat pumps rely on accurate sensor readings to resolve the issue.
If you’re still unsure, consult tech support for further guidance. Remember, a malfunctioning defrost sensor can lead to inefficient heat pump operation, so crucial to identify and address the problem promptly.
Verify Wiring Connections
Bad wiring can be the culprit behind defrost sensor failure.
You’ll need to inspect the wiring connections between the defrost sensor, defrost board, fan motor, and reversing valve.
Verify that all connections are secure and not corroded.
- Check the wiring diagram for your Lennox heat pump to confirm correct connections.
- Consult with a licensed HVAC technician if you’re unsure about the wiring configuration.
- Verify that the air conditioner’s wiring connections aren’t damaged or pinched.
- Follow expert tips from home repair pros and home improvement experts to avoid common mistakes during verification.
Also, Read: Lennox SL22KLV Heat Pump Error 104: High Pressure Detected in Outdoor Unit
Common Causes of Defrost Sensor Failure
Clogged pipes can shut down your system, leading to defrost sensor failure.
Failure to clear the pipe can lead to further damage, emphasizing the importance of regular maintenance.
A defrost sensor, a single throw switch, can open on temperature rise, but it’ll fail if not properly maintained.
The defrost sensor has a stamp (L80-30), meaning it opens at 80°F and closes at 30°F, and can fail if it doesn’t close when the outdoor coil is 30°F or below.
These common causes of defrost sensor failure can be prevented by ensuring your heat pump is well-maintained.
Expert Insights on Defrost Sensor Failure
You’ve likely identified the common causes of defrost sensor failure, now it’s time to hear from the experts.
They agree that understanding the intricacies of defrost sensor failure is vital in resolving the error code 106.
Experts emphasize the importance of having access to accurate information about the Lennox heat pump model and error codes for proper verification of the issue.
Knowledgeable experts stress that improper installation or maintenance can lead to sensor failure, highlighting the need for professional services.
They recommend regular checks to confirm the defrost sensor is clean and free from debris to prevent sensor failure in your home.
Also, Read: Lennox SL22KLV Heat Pump Error Code 103: Outdoor Unit Overcurrent Detected
Preventing Future Defrost Sensor Failure
To prevent future defrost sensor failure, vital steps must be taken.
Regular maintenance is key, including checking and cleaning the coil to reduce ice formation and confirm the heat pump operates efficiently.
Verify proper installation, including correct wiring and connection of the defrost sensor, to prevent future issues.
Replace the defrost sensor every 5-7 years, depending on usage and environmental conditions.
During installation, check the sensor specs and verify it’s not damaged or faulty.
Finally, set your thermostat to a reasonable temperature and avoid extreme swings to reduce the load on the heat pump and prevent overheating, which can lead to defrost sensor failure.
Also, Read: Lennox SL22KLV Heat Pump Error Code 101: Loss of Communication Between Outdoor and Indoor Units
Frequently Asked Questions
How to Tell if a Defrost Sensor Is Bad?
You’ll know a defrost sensor is bad by testing its resistance, voltage, and wiring; confirm proper sensor location and cleaning; check sensor calibration; and perform sensor troubleshooting to identify faulty sensor issues.
How Do I Fix My Heat Pump Defrost Mode?
You fix your heat pump’s defrost mode by identifying defrost cycle problems, troubleshooting faulty defrosting, and addressing defrost mode stuck or error situations, ultimately leading to a successful heat pump repair and defrost mode fix.
How Much Does It Cost to Replace a Defrost Control Board?
You’re wondering how much it costs to replace a defrost control board. The board replacement cost can range from $100 to $300, depending on the sensor module price and professional installation cost, which you can avoid with a sensor diagnostic tool and DIY repair guide.
Where Is the Defrost Sensor on a Heat Pump?
You’ll find the defrost sensor on the outdoor unit, attached to copper lines or coil, as shown in wiring diagrams. It’s a single-pole, single-throw switch, vital for the defrost cycle.
Conclusion
You’ve pinpointed the issue with your Lennox heat pump model SL22KLV, and now it’s time to wrap up. Error code 106 is like a red flag waving in your face, signaling a defrost sensor failure. Think of it as a domino effect – a faulty sensor sets off a chain reaction, crippling your system’s defrost mode. Don’t let it happen; stay proactive, and your system will hum like a well-oiled machine.
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