My AC is flashing an error code / blinking light — what does it mean and what do I do?
Our AC (split unit) has started flashing a light / showing an error code on the indoor unit or remote, and cooling is affected.
- What do AC error codes / blinking lights generally mean?
- Is there anything I can safely check or reset myself?
- When does it definitely need a technician?
I don't know the exact code meaning per brand. Trying to understand what it's telling me before I call. What should I do?
4 answers
Short answer: a flashing light / error code is the AC's self-diagnosis telling you a specific fault category — and while the EXACT code meaning varies by brand/model (check your manual or the sticker inside the indoor unit for the code list), the common categories are: SENSOR faults (a temperature sensor failed/disconnected), COMMUNICATION faults (indoor and outdoor units not talking — often a wiring/PCB issue), PRESSURE/PROTECTION trips (high/low refrigerant pressure — often a dirty condenser, low gas or airflow problem), and FILTER/maintenance reminders. First, note the exact code and count the blinks, then do the safe basics — clean the filters, check the outdoor unit isn't blocked/dirty, and power-cycle it (off at the isolator for a few minutes). If the code returns after that, it needs a technician; don't keep resetting a protection trip.
What the categories usually mean: - Sensor error: a temperature/coil sensor has failed or come loose — the unit can't read conditions properly. Technician (cheap part). - Communication error: the indoor and outdoor units aren't communicating — often a wiring, connection or PCB fault. Technician. - Pressure / protection trip: high- or low-pressure protection has tripped — commonly a dirty/blocked condenser, low refrigerant (leak), or restricted airflow. The system is protecting itself; find the cause, don't just reset. - Filter / maintenance reminder: some just want the filters cleaned and the reminder reset. - Fan/motor or defrost faults on some models.
What you can safely do first: 1. Note the exact code / blink pattern — and look it up in the manual or the code list on the sticker inside the indoor unit (brand-specific). 2. Clean the filters (a classic cause of airflow/pressure faults and reminders). 3. Check the outdoor unit isn't blocked, filthy or in recycled hot air. 4. Power-cycle: switch off at the isolator for a few minutes, then back on — clears transient faults.
When it needs a technician: - The code returns after the basics, or it's a communication/sensor/pressure fault → get an AC service and diagnostic. Repeated pressure/protection trips especially (dirty condenser/low gas) need diagnosing — don't keep overriding a protection trip.
Common mistake: repeatedly resetting the unit to clear a protection code without fixing the cause (dirty condenser, low gas) — you're ignoring a fault that'll get worse. Note the code, do the safe basics, and if it persists, get it diagnosed. Got a different brand? See Mitsubishi Electric, Panasonic, Hitachi, Haier, Hisense, TCL, Toshiba and Fujitsu error codes.
Anyone decoded their AC's blink pattern from the manual — what was it?
The code list on the sticker inside the indoor unit was news to me — flipped the front cover up and there it was, which turned a mystery blink into "communication error." Cleaning filters and a power-cycle at the isolator cleared a couple of transient ones for us over the years, but the persistent ones (sensor, comms) needed a tech. The advice not to keep resetting a pressure/protection trip is right; that one turned out to be a filthy condenser choking it. Note the code, do the basics, and if it comes back, call. Don't just keep hitting reset and hoping.
Power-cycling at the isolator (not just the remote) fixed a random error flash for us once — worth trying before panicking. But the recurring ones are the AC telling you something real, and resetting over and over just delays the diagnosis. Ours was a sensor in the end, a cheap fix once the tech read the code. The blink patterns mean different things per brand, so the manual or the inside-cover sticker is the key. Clean filters, check the outdoor unit, power-cycle, and if the code's stubborn, get it looked at rather than living with reduced cooling.
Seasonal note now the worst of the heat is passing: a lot of the codes people see are the system protecting itself in extreme conditions, high-pressure lockouts, over-temperature cut-outs, sensor faults that only trip when the outdoor unit is baking in 45-plus. As it cools those often stop appearing, which feels like the fault fixed itself. It didn't, the trigger just eased. So if your unit threw codes during the peak weeks, now is the sensible time to have it read and checked properly while you're not in a crisis, rather than waiting for the same fault to resurface next summer. And photograph the code before you clear it, it saves the technician a lot of guessing.
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