A portable AC that seems to have lost cooling power almost always has one of a few common, checkable causes.
Check the intake filter first
A clogged filter restricts airflow across the coil, reducing cooling capacity — this is the single most common cause of “it used to be colder” complaints across this family. See our cleaning guide for the routine.
Check the hose for kinks or excessive length
A crushed or sharply bent hose restricts exhaust airflow the same way a pinched straw restricts water flow, forcing the compressor to work harder for less result. Route it as short and straight as possible.
Check the window seal
A poorly sealed window kit lets warm outdoor air back into the room continuously, undoing a real share of the unit’s rated cooling. This is especially worth checking if the installation was improvised for a window shape the kit wasn’t designed for.
Check the room hasn’t simply outgrown the unit
If the room, its sun exposure, or the number of people in it has changed since the unit was sized, it may simply be undersized for current conditions rather than faulty — see our sizing guide.
What we would not do
Assume reduced cooling means a refrigerant leak or compressor fault before checking these more common, more easily fixed causes. In the large majority of cases across this family, the actual cause is a filter, a hose, or a seal — not the compressor itself.
The questions that keep coming up
When is reduced cooling actually a sign of a serious fault?
If the filter is clean, the hose is unobstructed and short, and the window seal is good, and cooling is still clearly below what the unit used to achieve, that's when a genuine refrigerant or compressor issue becomes more likely — at which point professional service is the appropriate next step, not a DIY fix.
Last reviewed 24 August 2026