i have just bought a used Haier HPAC9M portable AC, the previous owner said it has only been used for one season. i tried it at home, and the AC only works half of the time. It blows air alright, but only blows cold air for 5-10 minutes, then warm air for another 5-10 minutes, then back to cold air, then warm again. it goes on and on like this.
Possible a faulty thermostat .. or an incorrectly positioned thermostat..
Overload protector,
High presure cut out due to ..1). insufficient air
2). over charged.
3) Air in the system
low presure cut out due to 1). undercharge
2). restriction in the expansion device
The best advise I can give you is to take your aircon to a qualified technician....If you try to fix it yourself it might end up being more expensive..