Hi guys. This is my first time posting here.

I have a 99 E430 that is suffering an A/C problem. Basically, when I turn on the A/C no air comes out of the center vents. Instead the air blows out of the windshield vents. I played around with the computer console and nothing helped. I took the car to an MB dealer here in San Diego and they diagnosed the problem as having an incorrect PSE vacuum pump. According to the mechanic, due to this wrong PSE pump, the "actuator" that controls the center vents are not being controlled properly so air can come out.

Is the mechanic right regarding his diagnosis? Is this PSE pump easily replaced?

Thanks for any info.

Regards.