I noticed when I have the A/C button off that when I turn on the heater for partial defrost and floor heat setting that I hear the A/C clutch engage when I'm on heat mode and also the fans kick in as well when I know it is yet time for the fans to start ? and if thats so then why would it engage while the heat is on and the A/C button is off?

 

that is normal. defrost is also defog. the a/c system removes moisture from the air to make your windshield clear faster. mazda decided to do all the thinking for you and allow defog/defrost to turn the a/c system on without you specifically asking for it.