What are the most common issues with Audi A4 heating and cooling systems?

I recently purchased a used Audi A4 and have been experiencing some issues with the heating and cooling system. It seems to work inconsistently and doesn't always keep the interior at a comfortable temperature. What are some common problems that could be causing this and how can I resolve them?

One common issue with Audi A4 heating and cooling systems is a faulty temperature sensor. This can cause the system to incorrectly regulate the interior temperature. You may need to replace the sensor to resolve this issue.

Another possible problem is a clogged cabin air filter. This can restrict the airflow and make it difficult for the system to efficiently heat or cool the interior. Check and replace the air filter if necessary to improve performance.

If your Audi A4 is equipped with automatic climate control, the issue may be with the control module. This can malfunction and cause inconsistent temperature regulation. You may need to replace the control module to fix this problem.