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Appliance Error Codes

E10 Error on AO-SMITH NNLP-150-H NG Tankless Water Heater — Fix Guide

Error E10 on ao-smith : Combustion air fan motor fault. Follow the troubleshooting steps below to diagnose and fix this tankless-water-heater issue. ## What Error Code E10 Means on a ao-smith NNLP-150-H NG Error E10 on the NNLP-150-H NG tankless water heater indicates the combustion air fan motor is not running or is not reaching required speed. Without proper combustion airflow, the gas valve will not open. When E10 appears, the ao-smith tankless water heater pauses normal operation to protect internal components from potential damage. Not every E10 fault requires a professional engineer — many are resolved through careful inspection and routine maintenance. Work through each diagnostic step below in sequence, starting with the simplest check, to identify the root cause efficiently before considering part replacement or arranging a service call. ## Symptoms - E10 on display; unit will not fire

  • Combustion fan is silent when demand starts
  • Fan hums but does not spin (bearing seizure or capacitor fault)
  • Unit resets but E10 returns immediately ## Common Causes - Combustion air fan motor fault ## Tools You May Need - Multimeter
  • Screwdrivers
  • Replacement fan if needed ## Step-by-Step Repair Guide | Step | Action | Result | |------|--------|--------| | 1 | Power off the unit and locate the combustion fan inside the unit. | Done — continue to step 2 if the issue persists. | | 2 | Spin the fan blade by hand — if it is stiff, the bearings have failed. | Done — continue to step 3 if the issue persists. | | 3 | Restore power and measure voltage to the fan connector during the pre-ignition purge phase; should match the motor’s rated voltage. | Done — continue to step 4 if the issue persists. | | 4 | If voltage is correct but fan does not run, the motor is faulty; replace it. | Done — continue to step 5 if the issue persists. | | 5 | If no voltage reaches the fan, the PCB is faulty. | Done — if the fault remains, contact a qualified technician. | ## Safety Precautions Gas tankless units contain high-voltage ignition components. Service should be performed by a licensed gas technician or plumber. ## Estimated Repair Time and Difficulty Most tankless water heater error code E10 faults can be assessed and addressed in 30–90 minutes using the steps above. The diagnostic process requires only basic tools: a multimeter and standard screwdrivers cover the majority of checks described here. If a replacement part is required, allow 1–5 working days for delivery. A trained technician with access to the correct diagnostic equipment will typically resolve this type of fault within a single service visit. ## When to Call a Technician Contact a ao-smith authorised service technician if: the fault persists after following all the steps above; if PCB-level or refrigerant-circuit work is required; or if you are not comfortable working with electrical or mechanical components. When calling, have the full model number, the error code displayed, and a brief description of any sounds or symptoms you noticed before the fault appeared — this helps the technician prepare the correct parts and tools. ## Frequently Asked Questions Q: Can I replace only the fan motor without replacing the entire unit? Yes — combustion fans are a serviceable part. Use the OEM part number from the service manual for your specific model. ### Is it safe to keep using my ao-smith with error E10? If error E10 does not indicate an immediate safety hazard such as a gas leak, electrical short, or water flooding, you can continue limited use while monitoring the appliance. However, running the tankless-water-heater with an active error code increases the risk of further damage. Address the underlying issue as soon as possible. For high-severity errors, disconnect the appliance and contact a qualified technician. ### How much does it cost to fix error E10 on a ao-smith ? Repair costs for error E10 on the ao-smith tankless-water-heater depend on the root cause. DIY fixes such as cleaning filters, resetting the unit, or reconnecting loose wires cost nothing beyond basic tools. If a component replacement is needed, parts and labor from a certified technician are the main expenses. Contact a ao-smith-authorized service provider for an accurate estimate based on your specific situation. ### What does error code E10 mean on a ao-smith tankless-water-heater? Error code E10 on ao-smith tankless-water-heater models indicates Combustion air fan motor fault. This error is detected by the appliance’s internal diagnostic system and displayed to alert the user that attention is needed. Refer to the troubleshooting steps above for guidance on resolving this issue. ### Is it safe to keep using my ao-smith with error E10? If error E10 does not indicate an immediate safety hazard such as a gas leak, electrical short, or water flooding, you can continue limited use while monitoring the appliance. However, running the tankless-water-heater with an active error code increases the risk of further damage. Address the underlying issue as soon as possible. For high-severity errors, disconnect the appliance and contact a qualified technician. ### How much does it cost to fix error E10 on a ao-smith ? Repair costs for error E10 on the ao-smith tankless-water-heater depend on the root cause. DIY fixes such as cleaning filters, resetting the unit, or reconnecting loose wires cost nothing beyond basic tools. If a component replacement is needed, parts and labor from a certified technician are the main expenses. Contact a ao-smith-authorized service provider for an accurate estimate based on your specific situation. ### What does error code E10 mean on a ao-smith tankless-water-heater? Error code E10 on ao-smith tankless-water-heater models indicates Combustion air fan motor fault. This error is detected by the appliance’s internal diagnostic system and displayed to alert the user that attention is needed. Refer to the troubleshooting steps above for guidance on resolving this issue.