1996 Other Daewoo Models over heating problem

i have over heating problem with my daewoo espero car during summer season especially when i operate the air-conditioner.
- i don't have water leakage.
- the gas ket is very good (Ok).
- the fans are working properly.
- the over heat increases when i increase the speed.
- i checked the water pump it's working properly.
- the thermostat is opining completely.
- i cleaned the radiator many times (it is very clean).


i need a solution for my problem????

thanks

saad