Blowing hot air...or not

[socasa]

I have Punto. It's 51 reg so not new but not old. Never had a prob with the heating but now it's all gone dolally. Despite having plenty of coolant,etc only cold air comes out no matter what setting you put the heating at. On the rare occasions that hot air comes out, it suddenly goes back to cold if you increase the fan speed. Even when hot air does come out it's never as hot as it used to be.. Do you have any ideas why this coudl be? Fuse? Plain busted? Also, somethime the dials are soooooooo stiff i think i'll snap them. the next day they are as smooth as the day the car left the factory. What's that all about??

[chevrolet1.8]

if the problem is intermittent and the dial is stiff to turn it could be that it has become detatched behind the control panel it is fitted to. if it blows cold all the time it could be the thermostat stuck.

[socasa]

Thanks so much for your suggestions chevrolet1.8. I took the car to a garage yesterday and had it looked at . Imentioned to the mechanic what you had said. The mechanic agreed it could be either of the things you metioned. It actually turned out to be air in the system. The coolant wasn't getting around the engine and so the dials and engine were literally freezing up. Mechanic bleed the system and topped up again with coolant and now my car's a sauna and I love it!!