Can anyone help me understand the short cycling of portable air conditioners in small rooms? While it would make sense that an oversized cooling engine would cool down a room too quickly, that's not what's happening. With air temp of 75 degrees, and a set temp of 61 degrees, the compressor constantly cycles on and off every 4 or 5 minutes. Air temperature doesn't get close to the set temp until 5:00 am after running all night, when the outside air temp finally drops to the low 60s.

It's a very small room, about 140 square feet with 7.5' ceiling. DOE engine 7000-8000 BTU, can't get much smaller. 3 different brands, all new units, did same thing. I do raise the unit by putting it on a half-stack file cabinet (maybe 24-30" off the floor) to minimize exhaust run, and I do wrap towels around the exhaust hose. Otherwise, the heat loss through the duct approximately equals cooling.

Only thing that seems to make sense is they put the thermostat in the cold air duct. Compressor on, blow cold air on the thermostat. Don't believe any design engineer is that stupid. Any ideas what might be happening so I can correct it?