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164Heat pump needs service

Cross-checked High-voltage / caution

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Related diagnostic guides

Guide · Thermostat

Heat pump blows cold on heat (or warm on cool): O/B setting

The O/B terminal drives the reversing valve. Most brands energize it in cooling (O); Rheem and Ruud typically energize it in heating (B). A wrong O/B setting reverses the modes. Check the equipment diagram, not wire color.

4 steps ~20 mineasy

Guide · Thermostat

Auxiliary heat runs too much or all the time

Aux heat should only help when the heat pump cannot keep up. Constant aux usually means wrong wiring/settings (aux on the heat pump terminal, emergency heat left on), big setback recoveries, or a heat pump that is not producing heat.

4 steps ~45 minmoderate