Brivis fault code h01 56
Pressure switch stuck open, flue fan on but no pressure.
What h01 56 actually means
The pressure switch is stuck open. The flue fan is running, so the heater expects to see pressure in the combustion chamber, and the switch is telling it there is none.
What causes it
- Blocked or restricted flue, including bird nests and possum damage
- Flue fan running slow or failing
- Pressure switch tube blocked, kinked or disconnected
- The switch itself failed
- Water in the pressure tube after heavy rain
Most likely first. That order is from what we actually find on site, not from the manual.
Safe to check yourself
No tools, no covers off, nothing to do with gas, refrigerant or wiring.
- Nothing on this one. It is inside the cabinet and it is a gas appliance
- Turn the heater off at the controller and book it
What we check on site
So you know what you’re paying for.
- Flue inspection end to end, including the terminal
- Flue fan current and speed
- Pressure switch tube for blockage or water
- Switch operation tested against spec with a manometer
- Carbon monoxide test
Can you keep using it?
No. The pressure switch exists specifically to stop the heater firing when combustion products cannot get out. It is doing its job and it should not be bypassed or ignored.
What the fix usually involves
Frequently the flue rather than the switch: a nest, a crushed section, or a terminal that has come adrift. Where the switch or the fan has genuinely failed, both are stocked parts.
Is it worth fixing?
That depends almost entirely on how old the unit is. Past about ten years on hot water and gas heating, and twelve on aircon, a significant repair usually costs more per remaining year than a replacement does — and it’s the same point at which the VEU rebate is worth the most, because old inefficient appliances are exactly what the scheme pays to remove. If yours is young and the fault is a component, we’ll fix it and say so.
Repair or replace? The 10-year rule, and what the rebate is worth →