The F37 error code indicates low water pressure. It should not be there if your boiler is operating at around 2.4 bar. If it is there, there are two possible causes.
- Incorrect information is coming in to the main control board due to a failing pressure sensor;
- The pressure vessel is faulty.
Check the system by adjusting pressure to 1.5 bar and monitor it as the system is heating up. It should not exceed 2 bar when it heats up to the point. If it exceeds 2 bar too soon and continues to grow, the pressure vessel needs to be replaced.