Four-way valve failure: how it affects heating, cooling, and defrost

The four-way valve reverses the refrigeration cycle between heating and cooling and also participates in the defrost process.

Symptoms

Low efficiency, wrong operating direction, insufficient defrost, or abnormal temperatures in the exchangers simultaneously.

Electrical cause

Voltage may be missing at the coil or there may be a problem with the controller command.

Mechanical cause

The valve may not be moving fully or may be stuck internally.

Check

Verify the command and the actual change in temperatures/pressures in the refrigeration circuit.