43
Rheem
Pressure Switch Calibration or Airflow Fault
Status LED flashes 4 short and 3 long (43); furnace may short-cycle or not respond correctly
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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 for application, Vent length or configuration out of spec, Heat exchanger restriction, Control board misconfiguration
How to Fix / Troubleshooting
Safety first: Turn off power and gas before modifying venting or pressure components.
- Verify model and switch: Check that the installed pressure switch part number matches the Rheem furnace model and firing rate.
- Review venting: Compare actual vent length, diameter, and number of elbows to the Rheem installation manual. Correct any oversizing or excessive length.
- Inspect heat exchanger: Look for signs of rust flakes or blockage in the heat exchanger cells. A professional inspection may be required.
- Board setup: Some Rheem models require dip switch settings for venting or altitude. Verify these against the installation instructions.
Improper venting or pressure switch selection can cause unsafe operation; consult Rheem documentation or a qualified technician.
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Repair Difficulty
Professional Required
5/5
Required Part
Pressure Switch
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