9 flashes Pressure switch stays open or drops out on a heat call

What the control is telling you

The combustion air pressure switch did not prove within 2-1/2 minutes, or opened while running. The control goes into a 5-minute pressure switch Watchguard.

Applies to: EL195UHNE furnaces with ignition control 103217-03 or 107163-01 (red LED)

Likely causes

• Blocked or too-long vent/intake
• Plugged condensate drain or trap backing water into the header box
• Kinked, cracked or plugged pressure switch hoses or hose screens
• Weak inducer
• Failed pressure switch

Test and repair steps

1. Check intake and exhaust for blockage and that vent lengths are within Table 13.
2. Check the condensate trap and drain; a blocked drain backs water into the cold end header box and lowers the switch differential.
3. Pull the rubber hoses off the cold end header box and clean both the hoses and their screens.
4. Measure the differential across the inducer orifice with a manometer; the switch set point is 0.50 in. w.c. on all sizes.
5. Confirm the inducer runs at full speed; replace the switch only if differential is above 0.50 in. w.c. and the switch stays open.

Settings for these units

Filter sizes (filter rack kits) · Lennox EL195UHNE

Filters are field supplied; check monthly.

100NE60C over 1800 cfm with single side return needs a 20 x 25 x 1 filter via return air base and transition.

Models that show this code

4 models in Lennox EL195UHNE

Other codes on the same units

• 2 flashes Improper earth ground
• 3 flashes Burner failed to light or lost flame
• 4 flashes Low flame signal
• 5 flashes Watchguard - ignition retries/recycles exceeded
• 7 flashes Primary or secondary limit open
• 8 flashes Rollout switch open
• 10 flashes Watchguard - pressure switch opened 5 times in one heat demand
• 11 flashes Pressure switch stuck closed before inducer starts