HVACopedia

Lennox · Air conditioner

701 Thermostat temperature above limit

High severity

What the control is telling you

Thermostat reads above its fixed 99 F high limit. S30/S40 thermostat alert code 701.

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

Likely causes

  • Hot location or heat source near thermostat
  • Sensor fault

Test and repair steps

  1. Cool the thermostat / remove the heat source.
  2. Adjust set point.
  3. Run Reset All in the dealer control center.
  4. Change the HD display or the mag-mount as required.

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Source: Lennox Residential Communicating Systems Alert Code Guide (V2) 100017 (3/2023), Table 2 Alert Codes and Troubleshooting, p.47. Summarized in our own words; check the original manual for your model.

Homeowner looking at this code? See what it means for you and when to call a technician.

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.