When I stop or right after I take off at a light, I often hear a flap going somewhere under the dash. I assume it's that recirculation flap under the glove box.

So while I had the console panels off today, I looked at the rainbow of vacuum lines coming out of that manifold under the dash. I hoped I could access those lines better, but don't have the right tools to get the three cover screws off. You need a very special screwdriver to do this... Even worse, the airbag cars have a bracket on the drivers side that makes accessing those screws even harder (see pics)!

The lines all looked very clean and not brittle. Same the rubber connectors - all still soft and tight. I hooked the MightyVac up to the black line that goes into the manifold, and there was no measurable leakage.

Then I tried hooking it up to the yellow line, and got no resistance at all. But according to my WSM, the yellow goes somewhere I would probably not hear the flapping the way I do. I was not able to access any of the other rubber connectors, so I could not test the other colored vacuum lines.

Questions

- What is the trick to get this cover off. I know I had it off once on my first 928 (no airbag in that one), where it was more accessible. But I remember even there it was a real pain to get that center screw out! How have you accessed this in the past?

- If the yellow line shows no resistance, may I assume that the corresponding vacuum actuator is gone - or do they let the 'gas' pass when the ignition is completely turned off?

- Where would the actuator for the recirculation flap be located, and how can it be accessed? Remember, this is an airbag car that has the glove box under the dash!

Thanks!


Pictures show view from drivers side, then from passenger side

 

Brian and I did this. Brian posted some pictures and instructions.

https://rennlist.com/forums/928-forum/233165-no-heat-fixed.html

According to the WSM the yellow hose either controls the defroster flap (87-2) or the footwell flap (87-44)...?

 

Thanks, Bill!

Now, if I could figure out how to get that darn knee bolster bracket off, so I could at least access the screws of the manifold cover. I might have to find me some tool that turns screws at a 90 Degrees angle to get to the middle one - there is just no room, and i have no screwdriver that can accesss the middle or left ones.

But I still suspect that it's the actuators at the flaps that are bad, not necessarily the solenoids, since they are tight when testing the incoming line. Not sure, if I understand this correctly, though.

 

Nicole...........check out Jon Pirtles web site http://members.rennlist.com/pirtle/svc.html

The black line is the vacuum source from the engine bay, the other lines are:

blue.....recirculation flap (under the glove box)
green......defrost flap
orange......centre comb flap
yellow.......footwell flap
white.......hot water valve

There are screwdrivers made that are offset 90 degrees............check out the local tool store. Being of 'dainty' hands I could not get into this area without taking the radio and all out. Then I removed the centre console to get at the bad actuators................fun memories!

 

Nicole,

Check the black rubber connector has no cracks on the rear, or where the pipes enter. You will usually hear a slight hissing sound at one or two of the vent settings.

If they do leak, you'll need to replace with the part shown, using 90 degree screwdrivers to remove the centre screw as shown below. Might be easier to pull the console to replace this - my console was already out when I noticed the cause of my leaks. From the front the rubber connector looked fine, but was splitting on the rear.

 

Nicole,
Most of the problems I have encountered in the HVAC on my cars have been the diaphragms in the actuators.
One easy way to check them all is to use a box knife and cleanly cut all the tubes that are not easily accessible for checking.
You can then check them and reattach them with some plastic pipe over the outside diameter.
This means you do not have to remove the manifold at all. In future you can then check them in a few minutes.
Wally P has the best write up on checking the HVAC system. Go to 928 specialists and find Wallys World.

 

Nicole,
If you do feel you want to take the knee bolster off there is a nut inside the air duct at the far end of the dash. Pull the duct end cap and feel with your fingers. 10mm IIRC.

The actuators for the center vent and recirc are the hardest on an airbag car.
In fact the center vent is nigh impossible without major surgery - much easier on a pre airbag car.
If you have to do it I can walk you through the modifications that are needed to change it out.
Good luck
Roger

 

Nicole: You can get to the screw from the OTHER side of the console. I did not have to use a 90 degree, I believe, but Brian may recall otherwise. We did pull the radio out partway. Of course, you seem to have lot more crap crammed in there than Brian's earlier model, and the airbag gizmos make me nervous.

 

Hi Roger:

I have the knee bolster out already - it's that bracket that remains on the left side of the console that's in the way.

I like your tip about cutting and reconnecting the colored lines for easier diagnostics!!!

Bill:

I had the radio out and saw no way to get this screw out without a 90 Degree screwdriver.

Bert:

There don't appear to be any leaks going into the solenoids. I vacuum tested the line that goes into the solenoid manifold, and it has no measurable leakage.

 

Wally's HVAC packet has helped me. If you get a chance give a look

https://www.928gt.com/t-wallyhvac.aspx

 

Nicole,

At most Ace hardware stores, home depot, or walmart, they sell 1/4" drive bits separately for ratcheting screw drivers. They are very short and can be driven with a 1/4" or 7mm open or box end wrench.

Suggest a friend to get you one of these for XMAS:

http://www.overstock.com/cgi-bin/d2....cid=80543&fp=F

Actually, I have another nice $20 set that also includes many 1/4" metric sockets as well.

The center screw is very difficult to reach, and almost not worth replacing. However I did modify the black plastic tray under the solenoid valve in order to ease reassembly.

 

Got myself this today at OSH for $5 less than offered here:

http://www.homedepot.com/prel80/HDUS....jsp?pn=169380

I plan to look at the issue again tomorrow, after I had some time to think about what I'm doing there. It seems to me that it's not the electrical solenoids that are bad - it's the actuators at the flaps. Further diagnosis at this time is pointless, until I know where those acutators are physcially located and whether I could even access them without removing the dash. I certainly don't plan, nor would I have the time to take the dash out at this time.

Anyone have pictures showing where these actuators are located?

 

Nicole
Wow, your car looks even more cramped than mine! Judging from the flapping noise I would guess either (or both) the center comb flap (orange line) or recir flap (blue line) are leaking....One question? Does the flapping sound like it is coming from under the dash on the passenger side or from the center vent...& how about when you turn on the max A/C with the recirc on? It is a major hassle getting the center screw out of the HVAC console... Bill & I used a combo of a short stubby screwdriver and a screwdriver attachment to a socket wrench...which looked alot like that screwdriver mentioned...

I need to replace the recirc flap on my car too....the actuator is cheap...around $20...but you need to take ALOT of stuff apart to get at it! Your model will be harder since there is more stuff in there... Tony's page shows it pretty well here:
http://members.rennlist.com/v1uhoh/air.htm
Center comb flap here
http://members.rennlist.com/v1uhoh/combflap.htm
I still don't really know what the comb flap does besides break! Just close the manual lever on the vent seems to do about the same thing? I just cut and capped my leaking lines,
Pirtle site has it too
http://members.rennlist.com/pirtle/svc.html

Hmm....we might need to setup a recirc fix day? Older S4 (mine) & newer S4 (yours)...might be fun?

Bert
Good idea on replacing the main distrubution piece...I should have done that when I was in there...but it seemed okay?

 

Brian:

The flopping noise comes from under the dash, to the right of me. Based on that the yellow line seems to hold no vacuum, it could be the footwell flap. But it might as well be the recirculation flap. Now that I have this nifty tool to get that center screw out, I should be abel to diagnose - but tonight I have too much of a headache to deal with it. Maybe tomorrow...

Tony's description of the recirculation flap fix is great - I just don't know how different that would be in an airbag car. My glove box definitely blocks access to that flap area, and I have not yet figured out how to remove it - it's not obvious from looking at it.


Greggles:

I have an older copy of Wally's write-up, and wish it had pictures or diagrams of where these things are located. Obveiously, I know where the electrical solenoids are, but the actuators are so well hidden, someone needs to tell or show you where they are and how to access them.

 

Nicole,
Refer to Walley's write up and also look at the diagrams in the WSM section 87 P2 & P5. They will help a bit.
On your car the actuators are position as follows : -
Heater Valve - white line - under the air filter on the passenger side under the hood.
Defroster Flap - Green line - Directly above your right knee when sitting in the drivers seat.
Footwell Flap - yellow line - Behind the center console - easiest access of all.
Center flap - Orange line - Behind the center console just above and to the right of the footwell flap - this is nearly impossible to change on an air bag car. Can be done.
Fresh air/Inside air (recirc) flap - blue line - directly below the blower fan - fairly straight forward to replace, looks harder than what it is.

Cut all the lines that you cannot get a mityvac on as I have suggested above and find out which actuators need changing. Once you have done that I can walk you through what needs to be done.
Make sure you have also checked the vacuum reservoir and check valve near to the brake booster. Look at Wally's instructions on how to check these.
Let us know what you find out.
Roger