heating problem?

[Brando_#1]

Does anyone know what could be wrong with my car. A Vauxhall Astra Estate. When I drive on motorway the car is fine and as soon as I come off a motorway journey of say 2 hours the hot air stops coming out and it is changes to cold air. How much will this cost to get it fixed? How long does it take to fix?

Thank you very much for your help.

[bob57]

try checking if thermostat is working properly

if you take thermostat out and run the car for a short distance to see if you get hot air coming through if it is the thermostat it would just be a few pounds but remember do not run with it too long

[erimus1]

Do you mean hot and cold air from the heater?? - if so, the hetare works by passing hot wter throught the heeter box unit and matrix - if it is low on water then the first thing you will notice is that the heater is blowing cold air all the time. If water is fine then it could be the thermostat sticking or fan not cutting in (is it electric?) - I think what Brando is talking about is not actually the thermostat (which is mechanical and part of the coolant system), but the thermostat sensor which unscrews and is replaced for a few pounds - try this and/or the connection to it.
Good luck.

[qapmoc]

If it was a problem with the thermostat the reverse would happen, thats is it would be cold when travelling fast and hot when travelling slow, Are you sure that the water level is actually correct, this might also be a airlock in the heater circuit.

[stanleyman]

When on the motorway the engine is working hard and producing sufficient heat for the heater and radiator to dissipate. When you slow down and if the coolant thermostat that restricts the flow to the radiator is faulty then the engine becomes overcooled and you get a cold heater. Replace the coolant thermostat to maintain engine temperature regardless of speed. It is not a sensor for an electric fan.

[madein1978]

Sounds like either an Airlock or a knackered water pump, the pump is likely as its a weak spot on Astras.