Footwell actuator is one of my vacuum leaks (the other is centre comb flap which I can live without) so I got a new replacement.

Haven't lifted console yet but looks from write-ups as if it will be easier to just drop in new diaphragm from the new actuator to replace the leaky old one.

Have been fiddling with the new one to take it apart and I wondered if there are any tips for how to simultaneously press in the four clips holding the actuator halves together so you can take it apart? I've been wary of experimenting as I don't want to break anything on the new actuator! I could do with four hands... Is it a case of pushing them in one at a time and slipping something in the 'slot' to keep the clip pressed in?

Or is it in fact easier to completely replace the old actuator?

Thanks for advice,



I used 4 small screwdrivers to help depress all the little tabs. 3 Is actually enough I suspect. The lid on the actuator can is snug on there, so even after the tabs are moved back it takes a little push to get the cap off.

Note the orientation of the cap so you can pop it back on in the same position, and maintain your hose relationship.

Also be aware that there is a SPRING! inside under the cap. It may help the cover come off once you get the tabs loose and the cover unstuck a bit.

The comb flap actuator is right above the floor vent actuator, might be a PM item since you are in this far. Both of mine were leaking so the decision was made for me. The comb flap actuator is a little tougher than the floor vent, thanks to the way the end of the actuator arm attaches to the comb flap arm inside the heater box housing.

I used the excellent instructions on the Pirtle website, but still should have been taking pictures along the way. There are always a few tricks that the pro's seem to know already but aren't always instantly obvious to everyone.
The footwell flap is just forward of the HVAC control head, on the right side of the air box. No CE panel to remove, no black strip-Caulk to replace. Carefully remove the cover from the top of the old one, and you can work the rubber boot and the plastic actuator piston out. Replace the rubber boot with the one out of the new actuator

Bob Fuelleman


Hmm. I have the new actuator apart, but the plastic actuator piston is riveted to the metal arm. If I try to peel the new boot off the plastic part I'm worried that it will get torn.

You're absolutely correct. The boot slips off easily after I bent the arm slightly so it could come through the actuator base and let me take boot all the way off.

So when I expose the actuator behind the console (next step after lunch) is it a case of unclipping the connection to the old metal arm, and similarly bend it to bring up through old actuator before putting new boot on? ==> YES !!



You can use the new arm/piston/rubber diaphragm without having to slide the old off and the new on. To get the old arm out of the housing, bend the U at the end of the arm open slightly, and you can take the whole thing out. Do the same with the new one, insert it, then close the U at the end again to let it all work in the correct alignment.

It is possible to slide the old rubber section off the arm and install the new rubber part again without fear. It will come off pretty easily once the 20+years of vulcanizing gets loose.
Bob Fuelleman


membrane of the combo and footwell flap are the same as used in the vacuum actuator from Mercedes: a1248000375. It costs +/- 38 euro


Heater actuator diaphragms renewal and centre console removal.
1) For decent guides to this work, see Dwayne's A1 write-up: 

and John Pirtie's work:

Here's some extra tips I learnt doing the work:

  1. If you know for sure you have leaking diaphragms and inoperative heater flaps then leave the removal of your actuator pipes/solenoids until you have the centre console and wiring disassembled. This makes access to the screws holding the solenoids A LOT easier.
  2. Definitely remove ALL the solenoids and clean the brass electrical connections up to a shinny finish like new. ALL of mine were a rust colour and heavily corroded. I used a small file to shine the connectors back up. I also sprayed the electrical connectors for the solenoids in the car with a contact cleaner. Good to do the earth connector on the solenoid unit as well,
  3. With the centre console removed hoover all dust/hair/leaves and more out. Clean everything you can with a warm cloth and the same for the console. Then detail all the plastic parts and rusted screws etc. You may never see any of it after reassembly but it will make a big difference to some of the details on your car and improve the smell! People do notice these things if you ever decide to sell your 928.
  4. With so many electrical connections disconnected now is a great time to remove any corrosion and spray all connectors with a contact cleaner after using a clean toothbrush to remove any dust etc.
  5. With the centre console out, any repairs required are now easily accessed. Here's some pic's of what I did to repair the leather cover that was separating from the console due to dried out glue. I also repaired several breaks to plastic parts.
  6. With the comb flap. Once you've drilled you access hole in front of the actuator to access the lever connection and popped the linkage arm off, use a large piece of foam to wedge open the comb flap. This makes reassembly of the actuator linkage easier as the lever connector inside the heater box moves down and slightly forward which makes visibility for reconnection of the linkage easier.

    There's no doubt, the centre console removal and diaphragm actuator renewal is a challenging/long job, so leave plenty of time and the rewards are definitely worth it. Not too mention the fact that the value of your 928 keep son rising!

cheers, Dave.