When an air conditioner protects itself, its board stores an error code. Depending on the brand and the generation, the code shows in one of three ways:
- On the indoor display or the remote control: a letter and digits such as U4, H11, E1. Many remotes have a check mode that shows the stored code.
- As blinking lamps on the indoor unit: the operation, timer or heating lamp blinks a number of times; the count stands for a code in the brand's table.
- As LEDs on the outdoor board: usually the blink counts of two lamps of different colours.
One code, different meanings
There is no common standard: one brand's E1 is not another's, and within a brand a newer generation can give an old code a new meaning. Always look a code up for the right brand and, when you can, the exact model on the unit's label.
Before you look it up
- Write down the code (or count the blinks of each lamp) and the models on the indoor and outdoor labels.
- Note when the fault appears: at start, after running a while, or only on hot days - it narrows the search.
- Switch the power off for a few minutes and on again: if the fault comes back at once, it is a real fault and not passing noise.
Then look the code up in the brand's table; in the app, pick the brand and the model to get that model's own definition.
Safety: switch off both the indoor and the outdoor unit before opening a cover or touching a board; the capacitors on the outdoor board stay charged for a while after power-off - wait for the board's lamps to go out and measure before touching. Refrigerant and high-voltage work belongs to a certified technician.