Mini split and heat pump error codes are short letter-and-number messages — such as E6, P4, or U4 — that a ductless system shows when its control board detects a fault. The code points to the affected area: communication between the indoor and outdoor units, a temperature sensor, the condensate drain, the refrigerant circuit, or the compressor. That lets you tell quickly whether the cause is a simple homeowner fix (a dirty filter, a clogged drain line, a tripped breaker) or a job that needs a licensed technician. The catch: every brand uses its own code set, and meanings can vary by model — so the fastest path is to pick your brand below, find your exact code in its quick-lookup table, and confirm it against your unit’s manual.
How to read any mini-split error code
- Identify your brand and model (look on the indoor or outdoor unit’s label).
- Read the code from the indoor display, the wired controller, or the blinking LED pattern.
- Look it up in your brand’s table below, then do the safe first step.
- If the code returns after one power cycle, stop and call a pro.
Most brands group codes by their first character — for example, communication faults, sensor faults, and compressor/refrigerant protection each tend to share a prefix. The brand guides below break down exactly what each code means for that manufacturer.
Pick your brand
Choose your manufacturer for a lean quick-lookup table of codes, meanings, and safe first steps: