Add another Kicks to the list, just took it in for exact same problem, cold at 18C--hot at 18.5, with A/C still on. When I picked it up they told me they could not find anything wrong with it. So I took a service advisor outside with me and showed him exactly what was happening-- he agreed it should not be spiking like that --it should be gradual increase --He said he would check with the Nissan Tech Line .. waited 3 days, no call from the dealer, called them back, general discussion went, as far as we are concerned there is nothing wrong with the car, it was designed that way. Something to do with the " ambient temperature " and the car is working as it was designed to do. I told him that just because it is designed a certain way it did not mean it was correct. Was told to call the service manager on Monday, long story short-no help, Service manager told me it is out of the dealers hands, that now I must contact Nissan Canada. Then a file can be created.