Alarm Outdoor sensor TL1 faulty

What does 5203 mean?

The Heat Pump has detected a fault with the outdoor temperature sensor (TL1). This alarm indicates that the sensor or its signal cable has failed, is missing, or has short-circuited after multiple warnings.

• Outdoor sensor TL1 is missing or faulty.
• Signal cable to the outdoor sensor TL1 is disconnected, damaged, or short-circuited.
• Loose screw terminal connection on the I/O board for the sensor.
• Outdoor sensor TL1 is out of its normal operating range.
• Internal I/O board malfunction.

Click steps to track your progress.

1. 1

   Visually inspect the outdoor sensor TL1 and its connecting cable for any signs of damage or dislodgement.

2. 2

   Check that the signal cable is securely connected to both the outdoor sensor and the I/O board (if accessible).

3. 3

   Power cycle your Heat Pump by turning off its 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 investigation.