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Daikin · Furnace

EE5 Open fuse (short in low voltage wiring)

Medium severity Daikin DR96TN/DD96TN

What the control is telling you

The low-voltage fuse on the control board is open, usually because of a short in the 24 V wiring (thermostat, outdoor unit or accessory wiring).

Applies to: Daikin DR96TN (upflow/horizontal) and DD96TN (downflow/horizontal) two-stage 96% furnaces with 9-speed ECM motor, R-32 ready

Likely causes

  • Short in thermostat, outdoor unit or accessory 24 V wiring
  • Fuse failed

Test and repair steps

  1. Measure R to C if the transformer secondary shows 24 VAC but R-C on the terminal board reads only about 13 VAC, the board fuse is blown.
  2. Before replacing the fuse, find the short: disconnect thermostat and outdoor unit wires and check each run for a short to ground or between conductors.
  3. Repair the shorted wire (often a nicked thermostat cable or a shorted contactor coil), then replace the fuse with one of the same rating.
  4. Restore power and run heat and cool calls to confirm.

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Source: Daikin RSD6612304 (DR96TN/DD96TN service), 2 Stage Troubleshooting Codes, p.28-29. Summarized in our own words; check the original manual for your model.

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For licensed technicians. Gas, electrical and refrigerant work must be done by a qualified, licensed person. Shut off power and gas before servicing, never bypass a safety control, and follow the manufacturer’s manual for the exact model; it and local codes always take priority. HVACopedia is not affiliated with any manufacturer; brand and model names only identify the equipment.