Daikin fault code U0
Refrigerant shortage.
What U0 actually means
Refrigerant shortage. The unit has worked out there is not enough gas in the system to run safely and has stopped rather than damage itself.
What causes it
- A leak at a flare joint, the most common by a distance
- A leak in the indoor or outdoor coil
- Poor evacuation at the original install
- A leak at a service valve
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.
- Turn it off
- Look for oily residue around the outdoor pipework, which is often where a leak shows itself
What we check on site
So you know what you’re paying for.
- Pressure test and electronic leak detection
- Nitrogen pressure test where the leak is not obvious
- Weigh in the correct charge after repair and evacuation
- UV dye where the leak is intermittent
Can you keep using it?
No. Running low on refrigerant is what kills compressors, and the compressor is most of the value of the system.
What the fix usually involves
Find the leak, repair it, pressure test, evacuate properly and recharge to weight. Anyone who offers to just top it up without finding the leak is selling you the same repair again next summer.
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 →