Mitsubishi Electric fault code U2
Compressor overheat / oil shortage.
What U2 actually means
Compressor overheat, or the unit has detected an oil shortage. This is the most serious code in the Mitsubishi range and the unit has protected itself by shutting down.
What causes it
- Refrigerant charge low, which starves the compressor of cooling and oil return
- Outdoor coil badly blocked
- Outdoor fan not running
- A restriction in the refrigerant circuit
- A compressor already on its way out
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 the unit off at the controller
- Check whether the outdoor fan was spinning before you did, if you can do that safely from where you stand
What we check on site
So you know what you’re paying for.
- Full refrigerant charge check and leak test
- Compressor windings and insulation resistance
- Outdoor fan motor and capacitor test
- Coil condition and airflow
Can you keep using it?
No. Stop using it. U2 exists to save the compressor, and every restart after it works against that. A compressor replacement on a modern inverter split is usually close enough to a new system that we would quote you both.
What the fix usually involves
If we catch it early and the cause is charge or airflow, it is a leak repair and a recharge and the compressor survives. If the compressor is already damaged, we will tell you and price both the repair and the replacement so you can decide with real numbers.
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 →