Alarm Z1 hot water sensor TW1 faulty

What does 5239 mean?

The Heat Pump has detected a fault with the hot water sensor (TW1) for zone 1. This alarm indicates a failure or short circuit in the sensor or its signal cable after multiple warnings.

• Faulty hot water sensor TW1 or its signal cable.
• Loose screw terminal connection for the sensor TW1 on the I/O board.
• Short circuit in the sensor TW1 or its signal cable.
• Internal I/O board malfunction.

Click steps to track your progress.

1. 1

   Visually inspect the hot water sensor TW1'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 TW1 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

   Should the alarm continue, contact a qualified Bosch service technician for specialized assistance.