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Well after dealing with the heat on I decided to pull the center console apart.
Three of the actuators are not holding vacuum (mighty vac test.)
Heater valves shuts 100% when vacuum applied direct to it FYI. And have driven around with direct vacuum to valve and valve stays closed with no heat. Did that in winter.
We stock the diaphragms for the center and footwell actuators as well as the other complete actuators for defrost and recirc.
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Does it have the "Do It Yourself" manual transmission, or the superior "Fully Equipped by Porsche" Automatic Transmission? George Layton March 2014
928 Owners are ".....a secret sect of quietly assured Porsche pragmatists who in near anonymity appreciate the prodigious, easy going prowess of the 928."
Get the 3M ribbon of black super sticky window seal for the recirc airbox. You don't want a leak there...right above the fuse panel. Also, when I replaced the actuator I followed Stan's (MrMerlin) advice to remove the new lever arm attached to the new actuator and reuse the original. You'll see why this is an effective and easy way to go when in there. I tested the original actuator with Mytivac after pulling the recirc airbox out. Wouldn't hold vacuum at all. After replacing it I found all the other vent positions worked better, though I still get the flutter behind the center vent (but, oddly, only in summer). I have Roger's replacement diaphragms for center and footwell flaps (spring project). They are made of silicone, not rubber, so they should last longer.
Diaphragms for the center & footwell are $56 each (I rob them from an actuator made for another famous German car).
Defrost actuator is $56.56 and recirc. is $42.32.
Last edited by ROG100; 02-09-2015 at 06:27 PM.
Reason: Price changed
BTW, what rate of vacuum loss is acceptable ... if you pump it down with the Mity-vac should it stay at that reading for what ... hours? minutes?
I've replaced stuff that leaked down any amount after a couple of minutes, is that overkill?
You have to think of them all combined (or at least all the ones that will be active together). If all together they take a few minutes to leak down enough to change actuator state you should probably be good. You need them to hold vacuum long enough to they don't flip state when you aren't generating good vacuum - e.g. times when the throttle is significantly (if not wide) open. Often you will only notice this on a long steep ascent.
However once they start leaking - its only going to get worse so the results may not hold over time.
Diaphragms for the center & footwell are $56 each (I rob them from an actuator made for another famous German car).
Defrost actuator is $47.19 and recirc. is $42.32.
Roger, left you a VM. I'll need to order these when you have a moment. Thanks!
Roger is sending me the actuators and diaphragms. Thought I'd dig in tonight in advance. Then I thought I'd remove the dash entirely so I can repair some cracks. Great night in the garage!
Hello to all the members of this forum, it is impressive what can be learned here about the fabulous 928, the question is that I do not know if you can acquire the vacuum diaphragms of the actuator 92857330903, it sells complete when really what that deteriorates and gives problems is only the diaphragm, I would greatly appreciate your help in this matter, greetings to all.
We sell the diaphragm for the comb/center flap for actuator 928 573 309 03.
Our replacement diaphragm is made of current manufacture in fluorsilicone which is far superior to the old black rubber originally used.
02-04-2015, 09:50 PM
928 vacuum actuator diaphrams
George Layton March 2014
