Just an FYI: below is an image of the little fan inside the IHKA control unit...you can see how dust can build up on it...which is what can make it sound louder the older the vehicle gets. If you take a good look at the left vent on the front of your IHKA control panel...take note if it has a build up of dust. If it does, take a small brush (like an old toothbrush) and clean out that vent. That vent is where air is drawn in by the little fan:
Image below by: Mario
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Images below by: Farnarkler (fan is held on spindle by magnet only)
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