Why is my Hisense portable AC blowing cold air but not actually lowering the room temp?

The biggest issue you're facing is that single-hose portable units create a vacuum by design. For every cubic foot of hot air that hose pushes out the window, a cubic foot of air has to be sucked back into your room from somewhere else. In a small 36-square-foot space, that unit is essentially acting like a giant exhaust fan, pulling hot, humid air through the gaps in your door, electrical outlets, or ceiling fixtures. Cracking the door open acutally made it worse becasue you just gave that vacuum an easier path to pull in 30c air from the rest of the house.

You need to verify the temperture drop at the source to see if the compressor is actually working right. Stick a thermometer directly in the front vent where the cold air comes out. It should be reading at least 10c to 12c lower than the ambient room air. If the air coming out of the vent is 16c but the room stays at 28c, the machine is cooling fine, but your **thermal infiltration** is simply higher than the cooling capacity because of that negative pressure. Try running the unit in **Dry Mode** for a few hours. In humid climates like Thailand, the AC spends most of its energy stripping moisture out of the air before it can actually lower the temperature. High humidity makes 27c feel like 32c. If you can get the humidity down, the air will feel significantly colder even if the thermometer hasn't moved much. Also, make sure that exhaust hose is as short and straight as posible. Those plastic hoses radiate a ton of heat back into the room; if you can feel heat coming off the hose itself, wrap it in a reflective insulator or even a thick towel to keep that heat from leaking back in before it hits the window. If the vent temp isn't significantly lower than the room temp, you probably have a defective unit or a refrigerant leak. But in a room that small, it's almost always the single-hose design fighting against itself. You're basically trying to cool the outdoors by constantly cycling fresh hot air into your tiny space.

OMG I just joined beacuse I'm so stoked to finally have an AC unit in my room!! That vacuum effect thing is totally wild, I never whould have thougt about air being sucked back in through the outlets. Since you're using that Hisense model, does the display light stay on all night? I'm a super light sleeper and I was wondering if there's a way to dim those bright LEDs or if I shoud just put some black tape over them so it doesn't look like a neon sign while I'm trying to crash!

Seen this plenty. These new portables are basially space heaters that happen to blow a little cold out the front. Back when we used real window shakers—heavy steel units—the compressor heat stayed outside where it belongs. In a tiny 36-square-foot box, 12,000 BTUs is massive overkill. It’s likely short-cycling. It chills the air right at the unit's sensor, thinks the job is done, and cuts the compressor before the walls even stop radiating heat. You’re fighting physics with a plastic toy. If you can, swap it for a small 5,000 BTU window unit and you’ll acutally get that ice box feeling.

Check where you've acutally put the unit. If the back's jammed right against a wall or those curtains you mentioned, it can't pull enought air in to cool it down. I've seen 'em overheat and throttle the compressor without actually throwing an error code.

Also, try aimin' the louvers way up. Cold air's denser and sinks, so if you're pointin' it at your feet, the top half of the room stays a furnace. If you get that air movin' towards the ceiling, it'll mix better. It's a tiny room, so even a little pocket of trapped heat'll ruin the vibe.

Update: So I checked the placement like you guys suggested. The curtains were defintely blocking the intake and the vacuum effect was pulling hot air in from the rest of the house. I moved it out a bit and sealed the bedroom door better. It's finally a freezer in here! The 12,000 BTUs was just fighting itself before. Thanks for the help!