u/AN081098

Hi all,

I’ve got a 2015 Audi S3 8V with a heating issue that’s got me stuck.

Car takes 10–15 mins of driving before any warm air appears, and even then only on low blower speed. If I increase fan speed, the air gets colder. Turning A/C on makes it colder again even with high temp set.

I replaced the heater matrix thinking it was blocked, but no change. Old matrix flowed fine when tested. After replacement, both inlet and outlet heater pipes get very hot (around 80–85°C oil temp).

Other symptom: passenger vents are warmer than driver side, with heat gradually dropping across the dash.

Coolant temps seem normal otherwise.

Any ideas what could cause this on the 8V platform?