The window AC that cools less and rattles more: the filter, the rattle and the 'gas refill' trap

A window unit is a refrigerator-sized machine bolted into the one hole in the wall the weather comes through, and its two complaints - weaker cooling and a rattle that out-talks the television - are almost always the household's own five-minute territory, not a technician's. There is also a third problem this page prints with hard edges, because it is the one the trade's opportunist runs: the AC that 'needs gas topping' as a routine service, which is not how the machines work, and the sentence that saves a household its worst money is here in plain words.

The cooling loss, in the order it actually happens

1. The filters: the front grille's mesh catches the room's dust before the coils do, and a coated mesh is a strangled machine - air that cannot cross the evaporator cannot give up its heat, which is why the 'less cold' complaint and the visible grey felt are the same sentence. The habit is the whole fix: two weeks in high-use season, the unit off, the grille out, rinse, dry fully, return. Ten minutes that the coil's own lifespan bills you for at a year's omission.
2. The outside coils: the rear half of the unit lives in the outdoor air's own dirt - harmattan film, kitchen grease carried out, the compound dust - and the same strangling physics applies from the outside: the machine dumps its heat through those fins, and the felt on them is the heat with nowhere to go. Gentle rinsing of accessible fins with water (pressure washers bend the aluminium into foil, and bent fins stop the airflow - the desk prints the warning because the compound's washer-man loves this job too much), a soft brush along the fin lines, and the deep clean - the disassembly wash - is a service conversation on its own terms.
3. Then the room's own leaks: the window frame's gaps around the unit's cabinet, the door left open to the parlour, the heat load the ceiling's afternoon sun adds (the top-floor page below belongs to the same bill) - an AC cannot cool what the house keeps refilling with heat, and the foam and cloth weatherstripping around the chassis is the cheapest capacity upgrade in the room.

The rattle, which is four screws and a felt

A window unit's noise budget is vibration finding loose metal: the cabinet's own screws against the frame, the grille clips, the panel seams, and the chassis resting on a frame that has rotted or widened with years (a unit that sits proud in a loose hole sings with the compressor all day). The evening's fix: power off, a hand on each panel while someone starts the machine - the surface whose touch changes the noise is the guilty one - then tighten, shim with weatherstrip or folded rubber where the cabinet meets the frame, and let the loose panel seats have a bead of the adhesive felt the trade sells for exactly this. The noise that tightening does not touch - the grinding inside, the rattle that stays put with the cabinet braced - is the fan's bearing or the compressor's mounts, and that is the technician's hour; the desk draws the line at the panel, not the sealed system.

The water that suddenly appears indoors

Condensation is the machine's normal product - litres of it on a humid evening - and the unit is installed with a slight outward tilt so the drain finds the outside; what goes wrong is the drain path: the channel plugged with the dust-felt, the tray cracked from years, or the installation that settled level or inward over the years, in which case the water pools in the cabinet and exits at the room's side. The check is a cup of water poured into the drain path outdoors with the unit off - it should leave the way it came - and the correction, a packing shim under the cabinet's front edge to restore the fall, is a ten-minute job the household owns outright. A unit dripping in a storm is not leaking 'gas water'; condensation is the only water the machine makes.

The 'gas' paragraph, stated once, loudly

A sealed refrigeration circuit does not consume its charge - the system's volume is closed, and a machine cooling poorly with clean filters and clean coils either has a leak, a failing component or a control fault, all of which are diagnosis-and-repair conversations, not top-ups. The service that responds to any cooling complaint with 'just recharge it' without finding and fixing the leak is the trade's oldest short cut: the unit runs for a season, the same leak drinks the fresh charge, and the household pays the recharge twice while the compressor it never protected ages anyway. The desk's standing sentence for the quote: no charge without a leak test, no leak repair without the pressure test, and the honest technician's invoice names the fault it found, not only the thing it poured in.

The desk's standing rule

Filters every fortnight in the hot season, coils rinsed gently at each turn, the drain cup-tested before the rains' humidity peak, panels tightened the week the rattle starts - and the word 'refill', spoken without a leak diagnosis, answered with a second quote. The machine is simple; the service that pretends otherwise is the only part of it worth replacing.