My 300D has a Blaupunkt Laguna CD36 headunit. As of last night, I have XM radio with a Roady XT receiver, and have it wired up via the AUX connection with power coming from the cig lighter. Now, when the car is on, a whine is present over the speakers. When I'm accelerating, you can hear either the alternator or the turbocharger whining louder with higher RPMs. When I turn on the headlights or use the turn signals, the whine gets worse and more staticy, sometimes accompanied by a ticking if the turn signals are on. It only happens when trying to listen to XM over the AUX connection, or in the rare instance that I'm listening to AM. When I have the car off and the key turned to the ACC position, I can hear XM or AM clearly. Do I need to install some sort of noise cancellation device?

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'81 MB 300SD, '82 MB 300D Turbo (sold/RIP), '04 Lincoln Town Car Ultimate

Sooner or later every car falls apart, ours does it later!
-German Narrator in a MB Promotion Film about the then brand new W123.