A05
Hoval
Combustion air pressure switch fault
Furnace locks out with air pressure / air proving fault, burner fan runs but 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
Blocked combustion air intake on Hoval unit, Faulty air pressure switch, Split or blocked pressure tubing, Fan speed too low due to failing fan motor
How to Fix / Troubleshooting
Safety: Isolate electrical power. Do not bypass safety switches.
- Check air intake: Inspect the combustion air intake grille and duct for dust, plastic bags, snow, or other obstructions. Clear any blockage.
- Inspect pressure tubing: Locate the air pressure switch and its silicone tubes. Check for cracks, kinks, or water inside the tubes. Replace damaged tubing and ensure correct routing.
- Test pressure switch: With power off, remove the tubes and gently blow through the switch ports to ensure they are not blocked. Reconnect firmly. A multimeter can be used to check switch operation when the fan runs (qualified persons only).
- Check fan operation: Restore power and call for heat. Confirm that the combustion fan on the Hoval burner reaches full speed. If it is slow, noisy, or fails to start, the fan motor or its capacitor may need replacement.
- Reset control: After corrections, reset the fault on the Hoval controller and observe startup.
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Repair Difficulty
Medium
3/5
Required Part
Air Pressure Switch
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