RepairPal Certified shops can diagnose and repair your 1991 Mercedes-Benz 190E. They provide transparent pricing with a minimum 12-month or 12,000-mile warranty on repairs and services.
1991 Mercedes-Benz 190E Cant get my heat to shift to defrost to floor
This is likely a vacuum leak. Hands-on inspection is needed to diagnose the issue. Use this link to find a good shop near you.
https://repairpal.com/repair-shops
Alex