560sl center vents doesn't works

[300maniac]

on my '88 560sl my center vents do not have any airflow. All side vents work just fine. It stated doing this all of a sudden. Any help would be very helpful.:

MORE THAN LIKELY THE CENTER VACUME ACTUATOR HAS A LEAK.
VERY EXPENSIVE TO REPLACE 250 - 300. NOT A DIY PROJECT. IM TOLD YOU CAN PLUG THE LINE AND GET SOME OF THE AIR BACK IN THE CENTER. I HAD MY MECHANIC DO MINE AND ITS ABOUT 85% ABOUT HALF THE PRICE. BUT ITS COLD AIR!

[300maniac]

Thanks for your diagnosis. I should point out that both center vents sporadically fail to blow "any air / all mode" while side vents work all the time. I suspect blower motor but I am not sure. The blower motor often makes "bird chirpping" sound. When I hear this sound, center vents circulate. Are center vents and side vents operate with different blower motors? It may very well be combination of both blower motor and center vacume problem. Is this common with 560SL?

Thanks everyone

1 blower different outlets are vacume operated dampers to direct flow to the approiate outlets. Seems like a typical problem which is difficult to troubleshoot and no one likes to talk about it.