CODE 42
Fraser-Johnston
Inducer or Pressure Switch Stuck Closed
LED flashes four short and two long blinks; inducer runs continuously; no ignition.
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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
Pressure switch stuck closed, Shorted pressure switch wiring, IFC board sensing error, Inducer relay stuck
How to Fix / Troubleshooting
Safety first: Turn off power before testing switches.
- Test pressure switch at rest: With power off and no call for heat, disconnect one wire from the pressure switch and check continuity. It should be open. If closed, replace the pressure switch.
- Inspect wiring: Look for shorted wires between the pressure switch and IFC board.
- Reset control: Restore power and observe operation. If the inducer runs constantly and Code 42 persists, the IFC board relay may be stuck and require replacement.
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Repair Difficulty
Hard
4/5
Required Part
Pressure Switch
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