Air conditioning problems

The unit runs and the fan blows, but the air coming out is room temperature or barely cool.

Water is running down the wall below the indoor head, or dripping off its bottom edge onto the floor.

A damp, sour or gym-bag smell fills the room for the first few minutes after the unit comes on.

There is frost or solid ice on the copper pipes, on the coil behind the indoor grille, or on the outdoor unit's valves.

The indoor head is flashing its timer or operation lamp in a pattern, or the wall controller is showing a code like E4 or U0.

The indoor head blows air and the lights are on, but the box outside is silent and its fan never turns.

The system has become noisy — a rattle from the indoor head, a drone or vibration from the unit outside, or gurgling in the pipework.

Cooling fades after a few months, someone tops the gas up, and a season later it has faded again.

The system cools perfectly in summer but blows cold, or nothing at all, when you switch it to heat.

The unit ignores the remote, or the wall controller is blank, so you cannot change mode or temperature.