Air not always cool... why???

A little more info would be helpful but, based on what you have indicated, it sounds like it doesn't have anything to do with your HVAC blower resistor. This resistor only controls the different speeds on your blower motor not the temperature. If you are referring to the thermostat, that would control the temperature of your AC but would have nothing to do with the fresh air temperature. Does the AC air get colder when it is set to "AC Max" or "Recirc" Here are a few ideas that I could mention which may or may not have any bearing on your problem but, is a "best guess" while trying to read between the lines of your description. If the air does NOT get colder and the sound of your blower does not change when you select AC Max or Recirc, then the Recirculated air door is stuck, broke or the motor that controls this door is bad. Another item you might look at is the door that separates the HVAC evaporator from your heater core -- this door moves to block off the hot air flow from your heater core when you select COLD on your HVAC control and likewise, blocks off cold air flow from your evaporator when you select HOT. When you are somewhere in between HOT and COLD, the door moves to allow some hot and some cold air flow. If THIS door ( sometimes referred to as the "blend" door ) is not working properly, it could also be that the door or motor is stuck or broken or it could be that the controller is not sending the signal to move the door to the desired setting. Unfortunately, there are alot of different reasons that you are having this problem that are almost impossible to isolate like this but hopefully this gives you an idea of where to look next in trying to fix it yourself. Cost could be anywhere from $20 - $30 up to a few hundred depending on what it is that is failed. Hope this helps.

Thanks for your input, it's much appreciated. The fan blows just fine from low to high and when the AC air is at times almost freezing, I can regulate the temperature with no problem at all, it's just so inconsistent. For example today I left home (car in shade under carport) and the outside air came through very cool. By the time I got back into my car 2 hrs later, from being parked in the sun, the air from outstide came through warm even though it was still fresh outside. Re "Does the AC air get colder when it is set to "AC Max" or "Recirc"?... that's all works well ie more air coming through on Recirc, but again, only if the car is already cool? Yes I'm a mere female with little knowlede of cars but would it make sense that it comes in over the engine or similar which a male suggested? lol. What I do know is that it will probably cost me heaps eesh! I mentioned it briefly to my Mazda service man when last serviced and he didn't seem to have much knowledge about it "until we really get into it". Hmm pulling it all apart with many hrs labour I imagine : )

Ok, now we're getting somewhere. It sounds to me that your blend door is not fully closing off the hot air from your heater core ... It's difficult to illustrate how this is supposed to work in writing but I will give it a shot. Air flow from outside your car ( ie when your HVAC is set to "Fresh" air ) comes through the grill between your hood and windshield and into your HVAC blower housing. This is where your heater core ( which has hot engine coolant running through it ) and your AC evaporator ( which has cold refrigerant running through it ) are mounted. Both of these look like a small version of the radiator at the front of your engine compartment. The HVAC blower forces air through the fins of either the evaporator or the heater core or both depending on the position of the blend door. What youre describing seems to suggest that when the car is cold, the AC is cold but after it gets hot, the AC doesnt get as cold or not cold at all. What you can try to rule this out is ... in your engine compartment, there are two smaller hoses ( about the size of a garden hose ) that are connected to the engine and go through the firewall ( the partition that separates the engine compartment from the inside of your car ) -- These two hoses are the coolant hoses to your heater core. What you need to do is, get something like two pair of vise grip locking pliers and crimp these hoses so coolant cannot flow through them. Be careful not to damage the hoses or else you will have a coolant leak ! They are pretty tough hoses though so it would take some force to damage them. Now run your car as you normally do and see if it still acts up when it gets hot. If it does not, then the blend door is your problem. If it does still act up, it is probably the HVAC thermostat. One more thing you may want to look at is the electric fan in your engine compartment. Turn on your AC and open your hood. You after several minutes, you SHOULD hear your electric fan ( the AC condenser fan ) turn on -- if its not already on -- and then turn off. This electric fan is NOT the engine cooling fan but instead is the fan that draws air through the condenser to cool the AC system and lower the pressure. Hope this helps ( you being a "mere female" has nothing to do with it -- You are doing just fine ). I'm here to help as much as I can. -- Joe.

Thanks Joe, ur a gem! I'll give it a go. Cheers Gina ; )

Most of the mazda's have the same proble,fresh air is not as cold as the outside air is when the engine is hot.The blender door works fine,is fully closed,but the problem is somewhere else.i've read about a fis for mazda cx7 but I cannot find that TSB.It was said that they isntaled some new cmponent so the flower can get more fresh air from outside.I asked the dealer but thei do not knoe about it.If anybody now about that TSB please let us know so the dealers can fix this well nown issue with mazdas.thanks!

TSB 07-004/11 MAZDA CX7 AIR CONDITIONING NOT COOLING, there is also a video on youtube https://www.youtube.com/watch?v=1fPP4dZ8w1k