If you can identify the rubber pipes that go to the heater inside the car, these should both be good and hot if the water is circulating. Faults 1) a faulty on/off valve (if fitted) 2) The system needs bleeding 3) the coolant level is low 4) Flaps inside the heater not forcing air through the hot matrix. 5) the heater matrix itself is blocked with sediment. Usually the system just needs bleeding and to do this the top heater pipe is (very) gently removed and any air is allowed to escape - its then reconnected immediately. The Corsa may have other bleed points around the engine - I don't really remember - but popular places are around the top of the engine as this is where any air collects. If your heater pipes are still cold after all this, maybe the matrix itself is blocked. usually we have a go at clearing this by flushing the pipes through with a hosepipe.
John, December 2007
