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A121

A121 - Shutoff valve can’t open error

Rheem · Air Conditioning

What does A121 mean?

The internal shutoff valve is unable to open. This error message indicates a problem with the valve's operation, potentially disabling water flow control.

Common Causes

  • Shutoff valve malfunction
  • Wiring issue to the shutoff valve

Repair Steps & Checklist

Click steps to track your progress.

  1. 1

    Inspect the wiring connected to the shutoff valve.

  2. 2

    Try resetting the shutoff valve by unplugging and replugging it.

  3. 3

    If the issue persists, you will need to call customer service.

Browse all codes in this manual (48)
Verified technical data. Last updated: April 2026

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Source: Rheem Air Conditioning
Open Manual (Page 33)Search more codes in this manual