ac blowing hot air defrosting to on cold setting what should i test?

Hello! You could have a problem with the air conditioning system under the hood, or could have a problem with the temperature control mechanisms inside the vehicle. There is no way at all to test this without the proper test equipment or tools. I strongly recommend a properly trained and equipped technician near you. Here is a link to some possible local sources: http://repairpal.com/bmw-within-10-miles-of-kent-washington-98030