Refrigeration and heating

Good afternoon,

experience a phenomenon that was strange to me. I tell you, I have a Seat Cordoba 1.9 of 2005 (but talking to a colleague the same thing happens in a Volkswagen Golg VI). Well, yesterday the car was starting and we had an outer temperature of -6 °. I put the air conditioner to HI to heat the habitacle and take about 30 minutes to reach 90 ° in the refrigeration fluid but it worked. Until normal. However, when I reached 90 ° and the habitacle was hot I put the air conditioner at 22 °. At that time the refrigeration temperature descended to about 70 ° and that I do not think it is normal because when the demand for heating of the habitacle I suppose I should rise a little and then return to 90 ° but not cool.

I could explain to me whether that is normal or not and why?

Thanks

Foreto