MOD-BUS 251 — Communication error: Accessory is blocked

What does 251 mean?

Communication with an accessory has been missing for 15 seconds. A manual reset is required. Check the communication setup.

• Defective sensor
• Insufficient air circulation or blocked heat exchanger
• Defective control board in F2040/AMS
• Too much refrigerant

Click steps to track your progress.

1. 1

   Perform a manual reset.

2. 2

   Check the sensor connections and for defects.

3. 3

   Ensure adequate air circulation and clean heat exchangers.

4. 4

   Verify the control board and refrigerant levels.