EE9 High-stage pressure switch did not close

What the control is telling you

On a two-stage furnace the high-stage pressure switch does not close when the inducer goes to high speed. The furnace keeps running on low stage only. Flowcharts call this code E9.

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

Likely causes

• Pressure switch hose blocked, pinched or connected wrong
• Blocked flue or intake, or vent too long / too many elbows
• Blocked condensate drain
• Weak inducer on high speed
• Bad switch or loose wiring

Test and repair steps

1. Inspect the high-stage pressure switch hose and repair or replace it.
2. Check the flue and intake piping for blockage and for correct length, elbows and termination.
3. Check the drain system and front cover pressure switch.
4. With a manometer, compare the negative pressure at high inducer speed with the switch rating; enough vacuum but open switch = replace the switch.
5. Check inducer voltage and amps; replace the inducer if it cannot pull enough vacuum.
6. Tighten or correct the pressure switch wiring and retest a high-fire call.

Settings for these units

• Normal status displays (7-segment) · Daikin DR96TN/DD96TN