HVAC Code Lookup

Payne Furnace Code 43

WarningShown as: 4 short flashes, 3 long flashes

Low-heat pressure switch open while the high-heat pressure switch is closed - a contradictory pressure-switch state on a two-stage furnace.

Manual wording: “43 LOW-HEAT PRESSURE SWITCH OPEN WHILE HIGH-HEAT PRESSURE SWITCH IS CLOSED”

Documented for: PG96VTA

Likely causes, most common first

  1. Low-heat pressure switch stuck open
  2. Disconnected or obstructed pressure tube
  3. Miswired pressure switches
  4. Low inlet gas pressure (if LGPS used)
  5. Plugged condensate drain
  6. Water in the vent piping from a sagging pipe

What you can safely check yourself

  • Check the condensate drain line and trap for a clog or standing water
  • Check outdoor vent terminations for blockage

When to call a technician

Pressure switch wiring and vent piping slope are technician diagnostics. Never jumper a pressure switch.

A Payne furnace throwing this code repeatedly has a reason — clearing the code without fixing the cause just hides it.

Source

Other Payne codes