Ladies and Gents:

I just finished numerous projects on my 1989 300E: New Injectors, Fuel Filter,Oil and Filter change, and Replaced Aux Fan. During my post-maint. test drive, I turned on the A/C, and noticed that the vents are blowing cold air, through the middle two vents, and the outer vents (and center right) are blowing hot air like the heat is on full blast.

I am guessing some sort of vacuum flap problem, or perhaps some sort of heater(mono?)valve problem.

Did I unplug somthing by accident while working on the fuel distributor and injectors? Also, I disconnected and reconnected the Negative battery cable several times working on a fuel filter leak. Could I have tripped a solenoid of some type or popped some vital fuse?

Any guidance would be appreciated. The car runs beautifully with the new injectors, but it is 110 degrees in Phoenix right now! I need my A/C!! Help!!

Piece of cake, check it out here!

Monovalve Procedure!
Go here for a step by step with pictures R&R for a 126!

http://mbdieseldiy.tripod.com/index.htm

SOUNDS LIKE A VACUUM LEAK. TEST THE VACUUM SYSTEM FOR THE VACUUM ELEMENTS. CHECK TO SEE IF THERE IS ANY CORROSION UNDER THE BATTERY. THERE IS A VACUUM LINE IN THAT AREA. IF IT GETS A MINOR HOLE IN IT YOU WILL LOOSE VACUUM TO THE SYSTEM. THE HEATER VALVE IS SET UP TO GO TO HEAT MODE IF THERE IS A VACUUM LEAK. NO HEAT FROM CENTER VENTS IS A STANDARD ON ALL MB'S. THATS WHY YOU DONT HAVE HEAT THERE.

Dear,
Don't you have the owner's manual?
I do and I can tell you your car is just doing what has ment to do
by the MB people.
The center vents will allways blow cold air when open, it's made
that way.
So: don't worry.
Sorry I didn't answer any sooner: I just read your thread now!
Danny M.