Furnace LED shows code 43; unit may not modulate correctly or may stay in one stage.
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.
Possible Causes
How to Fix / Troubleshooting
Safety first: Turn off power and gas before altering any gas or pressure components. Do not substitute non-OEM pressure switches.
- Verify tubing connections: Compare pressure switch tubing routing to the Bryant wiring diagram on the furnace door. Correct any crossed or misrouted hoses.
- Check for recent part changes: If a pressure switch or gas valve was recently replaced, confirm the part number matches the furnace model and BTU rating.
- Inspect vent and intake: Ensure there are no restrictions that could cause abnormal pressure readings.
Calibration and modulation faults typically require specialized gauges and factory data. Have a qualified technician verify gas valve modulation and pressure switch operation.
Repair Difficulty
Required Part
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