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P1

P1 — High or low voltage protection

Lennox · Air Conditioning

What does P1 mean?

The unit has detected that the input voltage is either too high or too low. This protection feature prevents damage to the system's components.

Common Causes

  • Unstable power supply
  • Incorrect voltage supplied to the unit
  • Issues with the building's electrical wiring

Repair Steps & Checklist

Click steps to track your progress.

  1. 1

    Check the main power supply voltage to the unit.

  2. 2

    Ensure the unit is connected to a stable and correctly rated power source.

  3. 3

    Consult an electrician if the building's voltage is consistently outside the recommended range.

  4. 4

    Reset the unit by turning off power at the breaker for 30 seconds and then turning it back on.

Browse all codes in this manual (57)
Verified technical data. Last updated: April 2026

Related Faults

E0E0 — Indoor unit EEPROM error (MMDB Indoor Units)E1E1 — Communication error between indoor and outdoor units (MMDB Indoor Units)E3E3 — Indoor fan speed error (MMDB Indoor Units)
Source: Lennox Air Conditioning
Open Manual (Page 6)Search more codes in this manual