Heater fan stops on

[A8 Owner]

Hi, have a fault with my heater. It sounds like it could be the rest heater, as its not loud or fast running. When i say it wont go off, i mean you can take keys out lock it and still on. Only way to stop it, is to pull a massive fuse out. Located at front of the pass footwell behind the wood.
Is there other ways to narrow fault down? Is there a easy connector to unplug, or another fuse, that just stops that part of heater system.
Instead of losing all the heating, and normal heat fan.

Thanks for any help given.