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5206

Alarm Flow sensor T0 faulty

Bosch · Heat Pumps

What does 5206 mean?

The Heat Pump has detected a fault with the primary flow sensor (T0). This alarm indicates that the sensor or its signal cable has either failed or short-circuited after multiple warnings.

Common Causes

  • Faulty flow sensor T0 or its signal cable.
  • Loose screw terminal connection for the sensor T0 on the I/O board.
  • Short circuit in the sensor T0 or its signal cable.
  • Internal I/O board malfunction.

Repair Steps & Checklist

Click steps to track your progress.

  1. 1

    Visually inspect the flow sensor T0's cable and its connection point to the Heat Pump for any signs of damage or dislodgement.

  2. 2

    Ensure that any accessible screw terminals for sensor T0 on the control board are snug (do not overtighten).

  3. 3

    Power cycle your Heat Pump by turning off the dedicated circuit breaker for at least 30 seconds, then turning it back on.

  4. 4

    If the alarm persists, contact a qualified Bosch service technician for further diagnosis and potential component replacement.

Browse all codes in this manual (60)
Verified technical data. Last updated: April 2026

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Source: Bosch Heat Pumps
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