This could indicate a bad resistor or shorted wiring. A hands-on electrical test is needed.If you don't normally work on cars then use this link to find a good shop near you.
https://repairpal.com/repair-shops
Alex
RepairPal Certified shops can diagnose and repair your 2008 Mercedes-Benz ML350. They provide transparent pricing with a minimum 12-month or 12,000-mile warranty on repairs and services.