Ruud Emergency Heat Control Fault

Thermostat fails to detect or control a Ruud heat pump's emergency heat mode

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Safety Warning

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.

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Possible Causes

Incorrect system type configuration (set as AC instead of heat pump), Miswired AUX/E or W2 terminal, Blown fuse on indoor control board, Failed AUX/E output on thermostat

How to Fix / Troubleshooting

Safety: Turn OFF power to the indoor unit before adjusting wiring.

  • Verify system type: In the thermostat setup, ensure the system is configured as a heat pump with auxiliary/emergency heat.
  • Check AUX/E wiring: Confirm that the AUX/E or W2 terminal on the thermostat is wired to the correct terminal on the Ruud air handler or furnace that controls electric strips or backup heat.
  • Fuse inspection: Check the indoor control board fuse and replace if blown, investigating for shorts in the AUX/E circuit.
  • Manual emergency heat test: Switch the thermostat to EM HEAT mode (if available). If the system does not heat, but does when R is jumpered to AUX/E at the control board, the thermostat output is likely faulty and the thermostat should be replaced.
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Repair Difficulty

Medium 3/5

Required Part

Ruud EcoNet Smart Thermostat Assembly
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