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Garage => Interiors & Exteriors => Topic started by: SuitGuy on 05 July 2021, 04:01 PM

Title: Center Vent / ACCII Vacuum Issues
Post by: SuitGuy on 05 July 2021, 04:01 PM
So I may not be the most informed on the mystical wonders of ACCII, but I almost bet that my center vents should function! I'm able to get a thin screwdriver and gently pry up the main port and get ventilation to the center vents, but the vent will gently return to closed in a few seconds. I noticed that no blending occurs whenever I switch from DEF to Bi-level or any other option except maybe OFF (I.E, I never have center vents, always have defrosters and side vents). I'm not sure if this is normal, but I would really love some center vents. Anybody know if this is a control panel issue, or possibly a mismatched vacuum setup on my control panel?
Title: Re: Center Vent / ACCII Vacuum Issues
Post by: UTn_boy on 06 July 2021, 10:49 AM
Likely neither.  You probably have a bad/ruptured vacuum actuator that opens the center vent.  In addition, several of the other actuators are probably with ruptured diaphragms on the insides of them. 

The dash and/or the center console will have to be removed to get to most of the actuators.  And no, the aftermarket replacement for the ACCII won't fix the problem, either. 
Title: Re: Center Vent / ACCII Vacuum Issues
Post by: daantjie on 06 July 2021, 11:05 AM
Indeed as Aaron has stated likely you have vacuum leaks all over the show.  Best to invest in a Mityvac or similar style vacuum hand pump and get busy pulling vacuum to at least see where you have leaks.  The large actuator which controls the fresh air flap (blue in colour from memory) is a big culprit for leaks.  You will need to remove the knee roll and panels in the passenger side footwell to get access to it. This is a "fun" game of whack - a - mole unfortunately, no short cuts :-\
Title: Re: Center Vent / ACCII Vacuum Issues
Post by: Engineerd3d on 07 July 2021, 01:54 PM
I bypassed the front actuator door. I simply snuck a copper wire from behind the bled door and wired the center dash opened. Ac works much better this way. I had to remove the vents in the front to help me actuate it opened and wired it open. You can still close the center vent with the knob. Not sure why Mercedes chose to go this complex but this is the deal.
Title: Re: Center Vent / ACCII Vacuum Issues
Post by: SuitGuy on 07 July 2021, 04:47 PM
Thank you all. Sounds like I'm going to have a fun weekend pulling a vacuum system apart.
Title: Re: Center Vent / ACCII Vacuum Issues
Post by: UTn_boy on 08 July 2021, 11:58 AM
I bypassed the front actuator door. I simply snuck a copper wire from behind the bled door and wired the center dash opened. Ac works much better this way. I had to remove the vents in the front to help me actuate it opened and wired it open. You can still close the center vent with the knob. Not sure why Mercedes chose to go this complex but this is the deal.

Pre 1978 cars with ACC did not have the knob to close the center vents.