Google Nest · Thermostat error code

E58 / E108 / E188Overcurrent on the star (*) terminal

Single source High-voltage / caution

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Related diagnostic guides

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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

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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

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E5 / E25 / E75 / E155 / E255 / E405

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