43
Payne
Low Heat or High Heat Pressure Switch Fault (Two-Stage Models)
Status LED flashes code 43 (four short, three long). Furnace may short-cycle or fail to maintain temperature.
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Safety Warning
This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.
If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.
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Possible Causes
Incorrect pressure switch wiring, partially blocked vent, undersized or oversized venting, defective low- or high-fire pressure switch
How to Fix / Troubleshooting
Safety first: Turn off power and gas before adjusting or removing venting or pressure switches.
- Confirm model staging: On two-stage Payne furnaces, there may be separate pressure switches for low and high fire. Verify wiring matches the furnace wiring diagram.
- Inspect vent system: Check for sagging vent pipes that can collect condensate, improper slope, or partial blockages.
- Check pressure switch tubing: Ensure each switch is connected to the correct port on the inducer or collector box and that tubing is not kinked.
- Test switches: With a manometer or multimeter, verify that each pressure switch closes at the specified pressure when the inducer is running in the corresponding stage. Replace any switch that does not close properly.
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Repair Difficulty
Hard
4/5
Required Part
High-Stage Pressure Switch
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