3 double red flashes Second-stage pressure switch not closing

What the control is telling you

Two-stage boards (UTEC / White-Rodgers): the high-fire pressure switch stays open on a second-stage call. TM9V boards report this as 13 red flashes instead.

Applies to: York/JCI residential gas furnaces: York UTEC IFC furnaces, York White-Rodgers IFC furnaces

Likely causes

• Partly blocked vent or intake
• Inducer not reaching high speed
• Hose or wiring problem at the high-fire switch
• Faulty high-fire switch

Test and repair steps

1. Check vent/intake for partial restriction.
2. Confirm the inducer reaches high speed on a W2 call.
3. Check the high-fire switch hose and wires.
4. Test and replace the switch if it does not close.
5. To read stored codes with no thermostat call active, tap the LAST ERROR button briefly (under 5 s); up to five codes play back newest first. Two green flashes = memory empty. Hold the button 5 s or more to clear (three green flashes confirm).

Settings for these units

• Clearance to combustibles · York TM9V
• Filter size by return location · York TM9V

Other codes on the same units

• 1 red flash Flame detected with gas valve off
• 2 red flashes Pressure switch closed when it should be open
• 3 amber flashes W2 call without W1
• 3 red flashes Pressure switch open when it should be closed
• 4 amber flashes Cooling call (Y) without fan call (G)
• 4 red flashes Main limit switch open
• 5 red flashes Rollout switch open / limit circuit open over 15 min
• 6 red flashes Pressure switch cycling lockout