I have a Fiat idea but I suppose the problem I have could be very similar on many other fiats. The heater blower works ok but as you change the dial to cabin , screen ,vents etc the temperature varies from hot to cold and back but not always on the same dial settings,- any ideas. Dave

It could be there's a small delay, especially if you have the full automatic climate control, from the time you push the button until the system responds.

Also, there could be some cold air already in the system and this will be pushed out ahead of the heated air.

It seems to work ok until the dial is turned to one of the other outputs then it blows out cold air!