How can I fix the heater on my Mk 2 Astra?

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