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191

Alarm 191 - Inverter Voltage Mismatch

Lennox · PRODIGY 2.0 Unit Controller

What does 191 mean?

There is a voltage mismatch between the inverter and the system. Compressor operation will be disabled.

Common Causes

  • Incorrect inverter part installed

Repair Steps & Checklist

Click steps to track your progress.

  1. 1

    1. Power Cycle: Turn the unit's main power switch OFF, wait 60 seconds, then turn it back ON. This can reset minor glitches.

  2. 2

    2. Check Breaker: Locate your home's electrical panel and ensure the breaker for your Lennox unit is not tripped. If it is, flip it completely OFF, then back ON.

  3. 3

    3. Check Controller Display: Look for any additional messages or specific fault codes displayed on your PRODIGY 2.0 controller. Note them down if present.

  4. 4

    4. Call a Professional: If the alarm persists after these steps, or if you notice any unusual smells, sounds, or visible damage, contact a qualified Lennox service technician. This issue often requires specialized tools and expertise to diagnose and fix safely.

Browse all codes in this manual (56)
Verified technical data. Last updated: April 2026

Related Faults

12Alarm 12 - High Pressure Switch S414Alarm 14 - High Pressure Switch S716Alarm 16 - High Pressure Switch S28
Source: Lennox PRODIGY 2.0 Unit Controller
Open Manual (Page 139)Search more codes in this manual