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Lennox · Heat pump

E432 Inverter DC link high voltage (inverter code 28)

High severity

What the control is telling you

DC link capacitor voltage above 480 VDC; unit stops. 10 times in 60 minutes = lockout. Inverter LED flash code 28 (red 2 flashes, green 8 flashes). S30/S40 thermostat alert code 432 (shown as E432 on the unit control display).

Applies to: Lennox communicating heat pumps incl. variable-capacity inverter units in S30/S40 smart thermostat systems

Likely causes

  • High input voltage
  • Inverter fault
  • Compressor wiring or winding fault

Test and repair steps

  1. Check U, V, W connections at the inverter and compressor.
  2. Check compressor winding resistance and ground.
  3. Check input power single phase 208/230 VAC +10%.
  4. Check DC link and MICOM sensing voltage; replace inverter if out of range.
  5. Clear by disconnecting power to the outdoor unit and restarting.
  6. Check inverter LEDs flash code 28 = red 2 flashes, green 8 flashes. Normal inverter LEDs with no fault: red ON, green OFF.

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Source: Lennox Residential Communicating Systems Alert Code Guide (V2) 100017 (3/2023), Table 2 Alert Codes and Troubleshooting, p.37. Summarized in our own words; check the original manual for your model.

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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.