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E121

E121 — Motor PTC short-circuit

Wilo · VeroLine and VeroTwin Pumps

What does E121 mean?

A short circuit has been detected in the motor's PTC (Positive Temperature Coefficient) sensor, which monitors motor temperature.

Common Causes

  • Internal electronics error.
  • Motor PTC sensor is faulty.

Repair Steps & Checklist

Click steps to track your progress.

  1. 1

    Ensure the motor is not overheating.

  2. 2

    Check for any signs of damage to the motor's wiring.

  3. 3

    Contact customer service, as this likely requires professional repair.

Browse all codes in this manual (45)
Verified technical data. Last updated: April 2026

Related Faults

3 red flashes3 red flashes — Communication error6.0.0.0 flashes6.0.0.0 flashes — Ready to acknowledge error6.0.0.0 steady6.0.0.0 steady — Error acknowledgement countdown active
Source: Wilo VeroLine and VeroTwin Pumps
Open Manual (Page 52)Search more codes in this manual