On some Klarstein models, E7H appears and heating or cooling stops.

Safety: Isolate power before accessing the outdoor unit. The four-way valve is part of the sealed refrigerant circuit; do not open it.

Steps:

• Listen for switching: When changing between heating and cooling, you should hear a click from the four-way valve. If not, the coil may not be energizing.
• Check coil voltage: With power on and mode changed, a technician can measure voltage at the valve coil. If no voltage, suspect the PCB; if voltage is present but valve does not shift, suspect the coil or valve.
• Coil replacement: The solenoid coil can often be replaced without opening the refrigerant circuit. Replace with a compatible Klarstein coil.

Mechanical valve failure requires refrigerant recovery and valve replacement by a licensed technician.