Window units, sleeves and PTACs, translated

On a window unit the filter is behind the front grille and slides out in seconds. A blocked one halves what the machine can do and it is the single most common cause of this complaint. Wash it, dry it properly, put it back.

You are cooling the outside. The side panels and the seal at the top of the sash are the difference between a unit that copes and one that never will, and in a Yonkers apartment with old sash windows they are rarely intact after a few seasons.

Then the honest answer is that a service call on it is usually money wasted. There is very little worth repairing inside a window unit at this age, and the parts and labour approach the cost of a new one. We would rather tell you that than take the call.

A through-wall sleeve unit or a PTAC is different — those are worth servicing, and the sleeve itself is worth keeping.

A window unit is designed to sit with the outdoor end very slightly lower than the indoor end, so condensate runs away outside. Set level or tipped inwards, the water has nowhere to go but your floor. This is the cause most of the time and it is a bracket adjustment.

The coil is freezing and then melting faster than the pan can cope with. That is low airflow (filter, blocked coil) or low charge. Switch it off and let it thaw fully before running it again.

Different problem. The sleeve has a drain path and a seal where it goes through the wall, and when either fails the water goes into the wall rather than out of it. In an apartment building this becomes the building’s problem, and it needs reporting rather than mopping up.

Stop using it and unplug it. A warm plug means resistance where there should be none — a worn outlet, a loose terminal or a damaged cord — and that is how fires start. This is not something to keep an eye on.

Air conditioners should be plugged directly into a wall outlet. Most extension leads and strips are not rated for the current a compressor draws on start-up, and it is one of the most common things we see in apartments.

Either the circuit is shared with too much else, or something inside the unit is drawing more than it should. Either way the next call is to a licensed electrician, not to a heating and cooling contractor and not to a handyman. If you rent, it is also a report to the building, in writing, today.

We are saying this plainly because it is the one item on this page where waiting is genuinely dangerous.

Growth on a permanently damp evaporator coil and in the drain pan. Extremely common, and it is what the coil does when a unit cools in short bursts and never dries out.

Wash it and dry it completely. Then run the unit on fan only for a while at the end of the day so the coil dries — that single habit prevents most of this, and it costs nothing.

Then it needs cleaning properly rather than masking, and on a sleeve unit or a PTAC that is a job worth doing. We do not make health claims and we will not tell you what a smell is doing to anybody — that is a question for a doctor. We will tell you what is growing on the coil and what it costs to remove it.

The unit or the window is loose. Mounting brackets, the sash lock, the side panels and the bracket bolts are all things that work loose over a season, and tightening them is the whole repair.

Usually normal. Many units deliberately sling condensate from the pan onto the condenser coil to help it reject heat, and it sounds exactly like something wrong. If it happens only when it is humid and the unit is otherwise fine, it is the design working.

A fan bearing or a fan hitting something. On a window unit at any age this is normally the end of it. On a PTAC or a sleeve unit it is a repair and it is worth doing before it takes the motor with it.

The unit is too big for the room. Cooling and dehumidifying are two different jobs, and the second one only happens while the machine is actually running. A unit that satisfies the thermostat in four minutes never runs long enough to pull moisture out of the air.

This is the opposite of what almost everybody assumes, and it is why buying the biggest unit that fits the window is a mistake.

Confirmation of the same thing. People describe it as “it cools but it does not feel right”, which is exactly what an oversized unit produces.

This is the one moment where a short conversation saves real money. Capacity should be matched to the room, not to the window opening, and a smaller unit that runs for longer is more comfortable and cheaper to run than a larger one that short-cycles. We will say what size the room needs and we do not sell the boxes, so there is nothing in it for us either way.