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Lennox · Furnace troubleshooting

Blower motor does not run - Lennox SL280UHV ECM checks

What is going on

Variable-speed blower does not run; winding checks from the SL280UHNV service manual.

Likely causes

  • Damaged motor windings
  • Motor/control module failure
  • Harness or control problem

Check in this order

  1. Warning: Disconnect power before testing.
  2. Check the control display for E201, E202, E292 or E295 and follow that code.
  3. Test A measure resistance from each of the three motor leads (3-pin plug) to the unpainted end shield. Below 100k ohms = replace motor and control module; above 100k = go to Test B.
  4. Use an ohmmeter on the highest scale (100k or more) if not auto-ranging.
  5. Test B measure lead-to-lead resistance on the 3-pin plug; each pair must be under 20 ohms and all pairs equal. Over 20 ohms = replace motor and control module.

Applies to: Lennox SL280UHV (SL280UH070V36A, 090V36B, 090V48B, 090V60C, 110V60C, 135V60D) and SL280UHNV (SL280UH060NV36A, 080NV48B, 080NV60C, 100NV60C) 80% two-stage variable-speed communicating furnaces

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Source: Lennox SL280UHNV Unit Information Corp 1601-L8 (rev 04/2024), Troubleshooting Motor Windings, Table 14 and Figures 11-12, p.28. Written in our own words; check the manual for your exact model.

For licensed technicians. Gas, electrical and refrigerant work must be done by a qualified, licensed person. Shut off power and gas before servicing, never bypass a safety control, and follow the manufacturer’s manual for the exact model; it and local codes always take priority. HVACopedia is not affiliated with any manufacturer; brand and model names only identify the equipment.