Diagnosing and Repairing a Mitsubishi Ecodan Air Source Heat Pump – Fan Motors & Control Board Replacement

Diagnosing and Repairing a Mitsubishi Ecodan Air Source Heat Pump – Fan Motors & Control Board Replacement

At Burbage Heating & Plumbing Services, we were recently called out to investigate a fault on a Mitsubishi Ecodan air source heat pump – a reliable and popular renewable heating system designed for energy-efficient home comfort.

The system was displaying a U8 fault code, which typically indicates a communication or control failure between the system’s components. After a full inspection and diagnostic process, the fault was traced back to failed fan motors and a faulty control PCB (printed circuit board).

Common Signs Something’s Not Right:

• System not maintaining set temperatures.

• Unusual noises or lack of airflow around the outdoor unit.

• Persistent error codes such as U8.

• Increased energy consumption.

Our Diagnostic & Repair Process

1. Initial Checks & System Pressure Top-Up

We began by checking system health, topping up the pressure from 0.5 bar to 2.0 bar to ensure there were no flow issues or low-pressure shutdowns affecting performance.

2. External Inspection

Vegetation had started building up around the outdoor heat pump unit. Over time, this can reduce airflow and even damage the fins and components, so we advised the customer to keep the area clear.

3. Confirming the Fault

Using Mitsubishi’s diagnostic protocols, we confirmed the U8 fault and spoke directly with the manufacturer. Based on our findings and their recommendation, the fix was clear:

• Replace both fan motors

• Replace the main control PCB

4. Carrying Out the Repairs

Once the parts arrived, we carefully removed the damaged components and fitted the new fan motors and control board. The system was re-commissioned, tested, and set back into normal operation.

Why These Repairs Matter

Fan motors are essential to the efficient operation of air source heat pumps – they draw air across the heat exchanger to extract energy from the outside air. If they fail, the whole system struggles or shuts down completely. Likewise, the control board acts as the system’s brain – if it’s not working properly, even good components can’t function.

With these parts replaced and the area around the unit cleared, the system is now back up and running, delivering quiet, reliable, and efficient heating once again.

Is Your Heat Pump Showing Signs of Trouble?

We’re experienced in fault-finding and repairing all types of renewable heating systems – including Mitsubishi Ecodan, Viessmann, Nibe, and more. Whether it’s a minor service or a major component replacement, we’re here to help.

Please don’t hesitate to get in contact if your system needs a professional inspection or service.