Viessmann Refrigerant Flow Misrouting / 4-Way Valve Stuck (Heat Pump)

Indoor unit blows warm air in cooling mode even though compressor is running

This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.

If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.

Possible Causes

Reversing valve stuck in heating position, Faulty 4-way valve coil, Incorrect wiring to reversing valve, Internal valve leakage

Safety: Turn off power before accessing the outdoor unit. Refrigerant components should be handled by a technician.

Check mode wiring: Verify the reversing valve coil is wired correctly to the outdoor PCB.
Listen for valve shift: When switching between heating and cooling, listen for a distinct click from the 4-way valve. Absence may indicate a bad coil.
Measure coil voltage (technician): A technician can confirm the coil receives the correct voltage in the appropriate mode and replace the coil or valve if necessary.

Professional Required 5/5

4-Way Reversing Valve

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