2 Pressure switch stuck closed (did not open)

What the control is telling you

At the start of a heat call the control expects the pressure switch(es) to be open before the inducer starts, and found one closed.

Applies to: KeepRite (F/G)9MXE single-stage and (F/G)9MXT two-stage 95% furnaces

Likely causes

• Pressure switch contacts welded/stuck closed
• Blocked pressure tube holding the switch closed
• Miswired switch

Test and repair steps

1. Turn power off and check the pressure tubes for blockage or kinks.
2. With the inducer off, check the switch contacts for continuity - they should be open.
3. Replace a switch that reads closed with the inducer off.
4. Check wiring at the switch matches the wiring diagram.

Settings for these units

• Filter size by casing width · KeepRite (F/G)96VTN Two-Stage Variable-Speed Furnace

Models that show this code

16 models in KeepRite (F/G)9MXE Single-Stage Furnace, KeepRite (F/G)9MXT Two-Stage Furnace

Other codes on the same units

• 1+2 Blower running after power-up (normal)
• 3 Pressure switch did not close or reopened
• 4 Limit or rollout circuit open
• 5 Flame sensed with gas valve off
• 6 Flame not proved during ignition trial
• 6+1 Ignition lockout after 4 failed tries
• 7 Limit circuit lockout
• 8 Gas heating lockout - manual reset needed