My 1994 C220 does not blow air out of the center vents when it is hot (above 90) outside. The car has a new control panel which was replaced because the old one would short out. When it is relatively cool out, the system works perfectly. Any ideas what could cause this problem? Thanks!

This system has various sensors for outside air and inside air, any of which can be faulty.

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Benzmac:
Donnie Drummonds
1991 GMC Syclone
ASE CERTIFIED MASTER AUTO TECHNICIAN
SERVICE MANAGER FOR 14 BAY FACILITY
MERCEDES SPECIALIST 8 YRS
PARTNER IN MERCEDESSHOP.COM

The c-class cars use vacuum diaphrams to move the different a/c box doors, sounds as if at least one of these diaphrams is leaking vacuum. Also there is a vacuum storage tank & manifold that can leak. The vacuum control valve (a/c system) inside the car is the place to start.

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MERCEDES BENZ MASTER GUILD TECHNICIAN (6 TIMES)
ASE MASTER TECHNICIAN
27 YEARS DEALER M.B. Shopforeman
190E 2.3 ITS RACECAR
1986 190E 16V

Thanks for the help! Where is the vacum tank located for the A/C system? Can I tell if it is faulty by visually inspecting it?