I have a 2012 Mazda 5 that has been good thus far, except for one quirk.
I am not getting much heat in temps below -10c and I seem to get warm air only when I turn left. (no kidding) Will not even melt the ice on windsheild. Been to dealer three times now to little avail, but they are trying. Vent temp gets to aprox 33 degrees C., while warmed up,( set on max temp) when it should be 45 degrees C. or better, as does the identical service shuttle. The dealer has replaced the thermostat, rad fluid, checked all vents and valves for free movement and updated the computer something-or-other. Any thoughts out there on my quirky Mazda 5?

 

Sounds to me like you are having an external air blend with the heated air.

 

Would that explain the left turn heating? Weird!!

 

Maybe not, BUT you might look at the left side of the car as in if there is an external leak on that side it could be receiving warm air into it from the engine. Just a thought.

 

Could it be that the blend door or blend door actuator has been damaged? That's a common problem in Fords. When the door is disconnected from the actuator it may swing to the "heat" setting in left turns and go to "mix" or "fresh air" when driving straight and going right. I don't have a 5 so it's a guess, a point to check.

 

The dealership had the car again today and said they checked all the doors, vents and actuators. They had the dash apart. Everthything was free and working. The 5 is new, with no damage. One thing I did notice is that it takes 25+ minutes for the cold engine light to shut off @-10c. My wife's 3 takes about 15 min to come up temp.

 

I realize the tstat was replaced, however that would be the one thing I would do next. I can't relate this issue with Mazda as I've never had this experience. However I do have a 1996 Chevrolet Lumina that has a fail safe tstat in it that has failed open. When it's cold outside I can't get enough heat from the engine.

 

Well, -17c this am. Started the 5 at 0805 am and left it to warm up for 15 min befrore driving. Took 17 min for the cold engine light to shut off.
Drove until 08:35 and still had only luke warm air, unless I turned left or revved the engine up to 4,000 R.P.M. whereupon I got heat. Then, when I throttled back it retuned to the lukewarm temp again. This is one funky car.

 

What you post still points to the thermostat

 

Yes, Kevinpk is right: a bad thermostat will do that. Even new ones can be bad.