I have a punto SX 1998 model. Recently my heater has stopped getting hot where it used to be really fantastic - 5 mins in the car and you'd be toastie!
Resently I have had a prob with my electric cooling fan which has resulted in the car overheating and boiling over on a couple of occasions. It was after the last time that the heater in the car packed up.
The boil up stirred up a lot of sludge that is blocking the fine tubes in the heater matrix.
Air in the system.
Thermostat has disintegrated, or is stuck open. (that was my problem)
Kinked hose or heater valve stuck shut. (have had that, early valves used a rubber bung, later ones a gate valve.)
If the engine temp gauge is showing normal temp, the I'd open the heater tap, disconnect the two heater hoses, and see if you can flush water through the heater matrix with a garden hose. If that flows freely you know that the hot water can circulate. The pipes seem to be twin walled with reinforcing braid in between. The inner wall disintegrates, and the outside still look ok. As your car has over heated the hose may be the problem, hence the flush through test. Won't do any harm anyway.
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