My car is a 300CD Turbo, 209,000 miles. Rebuilt the vacuum pump, rebuilt the turbo-charger, and several smaller items. Then:

After reading dmorrison's superb DIY on replacing the induction unit I finished the project, including rebuilding the blower motor.
The fan works , all vents and vacuum modulators are working
well, but no air is coming through the box to the vents..
I cannot find any blockages??? I disconnected the heater core as it leaks, but I do not have occasion to use it here in S. Florida.
Today, after removing the blower, I'll feed a shop vac in blower mode into the blower opening just to see if the air can forced through the A/C box.
The dash is out in anticipation of removing the A/C box again, ouch.
Any ideas?? The induction unit is new, as are all important parts, and I was about to charge the system, but now am stymied.
All thoughts greatly appreciated.

you wrote:
"all vents and vacuum modulators are working"

and you wrote:
"no air is coming through the box to the vents"

please explain the differences and what's happening. thanks.

__________________
John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 190D 2.5Turbo
1987 190D 2.5-5SPEED!!!

1987 300TD
1987 300TD
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!

Hi vstech:

With the CC controller hooked up and power supplied, each button activates the appropriate switches (pneumatic at the front of the) and in turn the appropriate modulator is activated. They all work.

So, when I push the button with two solid arrows, the recirculating flap at the far right closes, the main flap opens and the center flat opens. The fan is on high speed and it works as well. I pulled the fan, attached it to a vise, and powered it, and it works well.

With all that, no air exits the center vent! ! I'm going to the garage in a few minutes to test it with the shop vac on blower now that I've cleaned it. I'll feed the hose into the fan housing (it is still out) and past the main flap to test if the passage is clear.

If necessary I'll pull the entire A/C housing (box) and open it, but now that it is back in - well, ouch. I am perplexed.

Oops, some typos there, center flap not "flat", and I refer to the pneumatic switches on a strip at the front of the box, or A/C housing.

Also, with new vacuum pump I have strong vacuum pressure, I replaced hose to the reservoir as it leaked.

What year??? I will assume a W123....This is critical because the climate controls change between body styles...

__________________
Did you just pass my 740 at 200 kmh in a 300SD?????

1978 300SD 'Phil' - 1,315,853 Miles And Counting - 1, 317,885 as of 12/27/2012 - 1,333,000 as of 05/10/2013, 1,337,850 as of July 15, 2013, 1,339,000 as of August 13, 2013



100,000 miles since June 2005 Overhaul - Sold January 25th, 2014 After 1,344,246 Miles & 20 Years of Ownership

Using a leaf blower with a hose attached, I pressured the opening for the MB blower motor and the vents gave produced only marginally more air.
Apologies, I should have used the term vacuum actuator instead of modulator in above description, my bad, sorry.

My 300CD Turbo is a 1983 with 209K miles and no rust.

Tomorrow, friday, I will remove the A/C "box" housing the fan, induction unit and heater coil. Good tim eto have the heater coil repaired.

After opening the housing and I hope finding the blockage problem I'll photograph it all for future edification.

Cya later

Hammer