I've just discovered a resource that you may need some day. My dealership was going to charge me $3500 for a new Command module for my '02 G500 plus labor. I looked at eBay, where I could get a used one for about $750. Then, I found Mid-West Electronics, the place where Mercedes USA sends its Command units to be repaired. If you send them your unit, they'll repair it, provide a 90 day warrantee and charge you $495. They claim that they'll turn the unit around in 2 days or less.

Mercedes COMAND Navigation Repairs

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