How can I get the heater in my Vauxhall Astra Mk 2 to provide warm air to the cabin instead of only cold. The blower is working fine and the engine is running at the correct temperature although the gauge hardly registers except in the summer.

Ian Stillwell, December 2005

I doubt that the previous answer of replacing the thermostat will fix your problem.
Usually the reason for no heat inside car at this time of the year is either.
1. Blocked water flow through radiator or heater matrix. Try a rad flush it may work if not replacement maybe needed.
2. damaged radiator water flow restricted through damaged fins.
Usually it's the heater matrix. At this time of the year the problem is evident because in the summer we don't use the heater. The matrix whilst not in use can become blocked.
I have known some people try caustic soda left in the system overnight and this has worked. If you try this it's up to you never tried it myself.

chris, December 2005

need to replace thermostat in engine then be fine

tony, December 2005