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