The hedgehog only controls the fan speed, when it fails the fan continues to run even with the ignition off. You'll know when it fails because you will constantly get a flat battery. Try a few bottles of injector cleaner to clear some of the crud, also a good hard blast down some fast roads will also help clear some of the soot especially if it's only been driven around town most of it's life. As for the heating do you have the digital control or dial control?