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Outbyte PC Repair FREERepair Windows errors before they cause bigger problemsFix Now →Outbyte Driver Updater FREEFix the driver behind crashes, sound loss and screen glitchesFind Drivers →Lennox error code 411 means the S40 Smart Thermostat detected five low-pressure-switch openings during one heating or cooling demand. Lennox classifies it as “Service Urgent” and says the thermostat shuts down the outdoor unit. The alert signals a protective shutdown; it does not, by itself, prove that the switch has failed or identify the underlying cause.
What Lennox error code 411 means
In Lennox’s S40 Smart Thermostat alert-code table, code 411 is listed as “OU Low Pressure Switch Strikes Lockout.” Lennox describes the condition as: “The low pressure switch has opened five times during one cooling or heating demand.” The five-opening threshold applies to a single demand, not to five separate system starts.
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After the threshold is reached, the thermostat shuts down the outdoor unit. Lennox marks the alert “Service Urgent,” so treat a recurring alert or continued shutdown as a reason to arrange qualified service rather than continuing to operate or reset the equipment.
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The alert reports repeated openings of a low-pressure safety switch. It does not establish that the switch itself is defective, nor does the code alone identify why the switch opened. Lennox’s listed diagnostic check is to assess system charge using approach and sub-cooling methods; those measurements require equipment-specific service procedures.
#1 Best Overall
- Genuine Replacement Component: 94W83 is a genuine replacement component designed for single-stage furnaces. This control board manages critical furnace operations, including ignition sequencing, flame sensing, and blower control, ensuring safe and efficient system performance. It operates within a voltage range of 18-30 VAC
- Wide Compatibility: 94W83 replaces older part numbers such as 81W11, 103085-01, 103085-02, and 103085-03. Ensure compatibility with your furnace model before replacement and follow all safety protocols during installation. This control board is essential for maintaining the reliable operation of your heating system
- High-Quality Manufacturing: Advanced microprocessor-based high-precision PCB manufacturing, soldering and assembly technology, professional tests to ensure optimal performance and long-lasting reliability
- Installation Tip: To save yourself some hassle, please take a picture of the old one before removing it to ensure getting the wires on the correct terminals during replacement
- Safety Precautions: Always follow manufacturer guidelines and safety protocols when installing or replacing furnace components; disconnect power before servicing to ensure safe installation
Because the code is not a component diagnosis, do not assume it confirms a refrigerant leak, airflow restriction, dirty filter, or any other particular fault. A technician needs the installed equipment model and system measurements to determine the cause.
What to do when the alert appears
- Record the exact alert. Note the wording and thermostat model; a photo of the display can help. Also note whether the system was heating or cooling and whether the outdoor unit is still shut down.
- Find the installed equipment model. Check the outdoor unit’s nameplate, then use Lennox Product Manuals and Literature to look up documentation by product category or model number. Confirm the alert against the manual for your thermostat and equipment; code definitions should not be assumed to apply to every Lennox control.
- Arrange qualified diagnosis if it recurs or the unit remains off. Contact a qualified Lennox dealer or HVAC professional. Lennox’s Support Center provides a local-pro lookup.
Should you reset Lennox error code 411?
Lennox says the alert clears automatically when the system detects that the issue no longer exists. Its S40 table also lists resetting low-voltage power or placing the outdoor-unit control in test mode as ways to clear the alert. These are code-clearing details, not repairs and not a recommendation to bypass repeated protection trips. Do not repeatedly reset the system instead of arranging diagnosis.
Rank #2
- Manufacturer Authorzed 32M8801 Furnace Control Board Direct Replacement for Lennox 50A65-121 White Rodgers Integrated Fan Control Circuit Board
What not to attempt as a homeowner
- Do not handle refrigerant or attempt pressure testing or charge adjustment.
- Do not use dealer-only control procedures as a substitute for diagnosis.
- Do not buy or replace a pressure switch based on code 411 alone; the alert does not identify a failed part.
Use the exact alert, the thermostat and equipment models, and the heating-or-cooling context to guide the service call. Lennox’s model-specific documentation and a qualified technician’s measurements are the appropriate basis for diagnosing the shutdown.
Quick Recap
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- We have local stores and can deliver your products as soon as possible. All products come with a one-year warranty.
- 100870-03
Rank #4
- 【Compatibility】The 94w83 furnace control board is specifically designed for the Lennox single-stage gas furnace system. It can be used as a direct replacement part for the original factory components, and the compatible models include 81W11, 103085-01, 103085-02, 103085-03, and 1012-977A-I.
- 【Control Function】It uses a microprocessor to achieve precise control, including ignition sequence, flame correction sensing, and delay control of the blower motor. It enables rapid startup and maintains a safe, stable, and efficient operating state.
- 【Easy Installation】The clearly marked terminal connections enable each user to complete the installation easily. It is recommended to take photos of the wiring before removing the old control panel to ensure the accuracy of the new connections and reduce the risk of installation errors.
- 【Durable Materials】It is made of high-precision PCB circuit boards, industrial-grade long-lasting relays, and precise welding techniques, featuring excellent anti-interference ability, electrical stability, and durability.
- 【Working Voltage】It supports a wide voltage input range of 18-30VAC, enabling it to maintain stable operation even when facing voltage fluctuations.
Rank #3
- 【COMPATIBILITY】Compatible with Lennox and White Rodgers models.
- 【MODEL REPLACEMENT GUIDE】Directly replaces models including 32M8801, 10M9301, 12L6901, 56L8401. For these models, follow Program 1. Also compatible with other models requiring Program 2 or 3. Confirming the correct program in the manual is essential for a successful installation.
- 【PACKAGE INCLUDED】1 * Ignition Control Board, 1 * Wiring Harness (9-pin to 12-pin), 1 * Wiring Harness (4-pin to 6-pin), 1 * Mounting Panel, 4 * Stand-off Fasteners, 1 * Circuit Breaker, 1 * 4" Blue Wire, 2 * Wiring Diagrams (for Programs 1 & 2), 1 * Instruction Manual with Diagnostic Chart.
- 【INSTALLATION & TROUBLESHOOTING TIPS】 For a successful installation: (1) First, confirm your required Program (1, 2, or 3) in the manual. (2) Photograph all original wiring before disconnecting. (3) Replace the old circuit breaker with the new one provided. If the system locks or shows errors: (4) Try a full power-off reset or wait 1 hour. (5) For persistent issues, use the professional Diagnostic Chart in the manual to identify causes, which may point to other components. (6) For safety and accuracy, professional installation is strongly advised.
- 【ATTENTIVE SERVICE】If you have any questions before or after purchasing, please feel free to contact us. We work hard to manufacture high-quality products and also work hard to treat every customer with care. Thank you for your choice.
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