Air conditioner gets cold then warm .....works good at night

Hello, You could have a problem with high pressure during the warm days (too much refrigerant or restriction in the system), but to be honest, there is no way to find out without having it connected to a set of gauges during a hot day. The things you can do before taking it to a professional A/C repair person are cleaning the radiator and condenser, and making sure the cooling fans are running when the A/C is turned on. After that, time for A/C diagnosis.