How can I fix the heating issues in my 1990 Audi 80?

I have been experiencing difficulties with the heating system in my old Audi 80. The heater does not produce heat consistently and sometimes it even blows cold air. I have checked the coolant levels and they seem to be fine. What steps can I take to fix this issue?

First, check the temperature control valve, as it may be stuck and causing the issue. If that doesn't work, try flushing the heater core to remove any blockages. If the problem persists, it could be a faulty heater control valve or a malfunctioning thermostat.

Have you checked the heating core? It may need to be replaced if it is clogged or damaged. Another possible solution is to bleed the air out of the system, as air bubbles can cause inconsistent heating.