HVACopediaDaikin · Furnace
EE8 High-stage pressure switch closed at start of heating cycle
What the control is telling you
On a two-stage furnace the high-stage pressure switch circuit is already closed at the start of a heat call. The furnace runs on low stage only (inducer still operates). Flowcharts call this code E8.
Applies to: Daikin DR96TN (upflow/horizontal) and DD96TN (downflow/horizontal) two-stage 96% furnaces with 9-speed ECM motor, R-32 ready
Likely causes
- High-stage pressure switch contacts stuck closed
- Short in the pressure switch circuit wiring
Test and repair steps
- Power off, remove the wires from the high-stage pressure switch and ohm the contacts with the inducer off - they must be open.
- Replace the high-stage pressure switch if the contacts are closed with no vacuum.
- If the switch is good, find and repair the short in the switch wiring.
- Retest a high-fire call (W1+W2) and confirm the furnace stages up.
Settings for these units
- Normal status displays (7-segment) · Daikin DR96TN/DD96TN
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Source: Daikin RSD6612304 (DR96TN/DD96TN service), 2 Stage Troubleshooting Codes, p.28-29; Error Code E1, E2, E8, E9 flowchart p.36. 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.