86-89 Carrera w/out AC -- what comes out the dash vents?

tubwreck · 05-06-2005, 01:08 AM

I've got an '88 that I'm removing the AC from. I haven't removed the evaporator and fan housing from the car yet, partly because I'm not sure what the air flow should be after removing it.

As I understand it, the evaporator fan draws air from the footwell area, cools it, and then blows it out the four dashboard vents. This happens whenever the AC is on.

The fresh air blower, the one controlled by the blue slider switch on the climate control panel, draws air from outside of the car (under the windshield) and blows it either through the defroster vent above the dashboard or into the footwell (depending on how the middle slider knob is set.

What I would like to do is make my car look (and operate) like a stock '88 without A/C (e.g. like a Club Sport).

My question is: on a stock 86-89 Carrera (the years with the bigger dash vents), what -- if anything -- comes out of those dash vents? Is there a connection between the fresh air blower and gthe dash vents?

racerdoc911 · racerdoc911's Garage

i removed the a/c on my 87, and I can confirm that nothing comes out of the dash vents. There is no connection between the F/A blower and the dash vents. Just do a search, there is lots of info on this subject.

tubwreck · 05-06-2005, 04:05 AM

I'm sure nothing will come out after I take out the AC.

What I'm wondering is, on cars that came from the factory without AC, such as the '88 club sport, what if anything are the dash vents used for? I would have thought they might have been connected to the fresh air ducting...

Noel · 05-06-2005, 04:45 AM

Anyone with a Club Sport or non-AC car care to comment? I'm curious about this also, since I removed my AC this winter.

KTL · 05-06-2005, 05:37 AM

To get air to come out the dash vents, you need to have something connected to the hoses that were previously connected to the condensor (is that what it's called?) blower assy. in the front trunk smuggler's box.

That the only reason I left that thing in the smuggler's box. Without those dash vents blowing ambient air on you, it can get pretty hot in there. But all you have to do is roll down the windows. Yet at highway speeds, the wind noise and turbulence from having the windows down can get tiring on a long drive.

Noel · 05-06-2005, 05:50 AM

So the question is "Do the Club Sports and cars without AC have their hoses connected to the fresh air fan?" If so, I woun't mind getting the part number of the piece that connects all of those hoses, so I can modify mine in a similar manner.

KTL · 05-06-2005, 05:57 AM

I tried a PET search. But I can't find where the A/C stuff is located!!!

tubwreck · 05-06-2005, 08:08 AM

What's a PET search?

KTL · 05-06-2005, 09:51 AM

PET is the Porsche parts software.

BTW, that box in the smuggler's box is called the evaporator. I mistakenly called it the condensor.

Found some A/C component info in the 1974-89 Porsche Parts and Technical Reference Catalog, circa Dec. 1995. But it only calls out the part #'s for the A/C components. No info on ventilation hoses.

I may have to resort to the lowly microfiche to get to the bottom of this!

RallyJon · 05-06-2005, 10:01 AM

Get a couple of these "Y" fittings (part #91157103900), some hose and a couple of clamps and I'm sure you can get air to those vents.

nut11 · 05-06-2005, 10:13 AM

I'm very much interested in how to get directed fresh air from the dash vents w/o keeping the evaporator assy in. I, too, have removed all other A/C stuff. The existing fresh air from the slider mechanism really doesn't cut it as nothing can be directed to your face or body. Thanks for any input.

85 Coupe (baby)

tubwreck · 05-06-2005, 10:27 AM

Should you disconnect the fresh air hoses from the mixing boxes and connect them to the dashboard vents, or do you insert the Y and and cause fresh air to both flow to the mixing boxes and to the fresh air vents?

tubwreck · 05-06-2005, 10:28 AM

Oh, and RallyJon, where did you get that nice diagram and can you post the rest of it -- the Bentley is vary vague on hose routing.

Mysterytrain · 05-06-2005, 10:34 AM

The side vents have plastic wye connectors that route heated air (from the footwell blowers) and A/C from the evaporator into the cabin. The center dash vent needs to be re-plumbed to get fresh air from the fresh air blower. I think you need to look at the PET drawings for SC's because air was still an option back then. I don't think heated air was ever channeled out of the center vent. There is a factory duct spliter on the early models that splits the fresh air that is going to the passenger side of the car to both the deforster/underdash vents and that center vent. Of course, when you got a/c on the early models they removed the spliter sent the air to the center vent and side vents and the fresh air came out of the deforster vents and the under dash vents where it could be mixed with heat. With the Carrera you got the footwell blowers and both a/c and heat from the larger side vents (no fresh air there as I recall) and A/c only from the center vent. Hope that makes some sense.

RallyJon · 05-06-2005, 10:43 AM

Ed, get it here: http://www.pelicanparts.com/cgi-bin/ksearch/pel_search.cgi?command=DWsearch&description=U-043-400-05&I1.x=13&I1.y=3

jmarenas · jmarenas's Garage

http://members.rennlist.com/imcarthur/ahoverview.htm

tubwreck · 05-07-2005, 05:42 PM

So I went out and poked around under the hood and dash of my car. I drew the following sketch which I think describes the air distribution system at the front of the car:

The top slider lever on the dash opens and closes the outlet valves (in tandem) on the fresh air blower.

The middle slider lever on the dash moves the two distribution flaps (on the blue sides) in tandem to direct fresh air up or down.

The bottom slider lever on the dash moves the two distribution flaps (on the red sides) in tandem to direct heated air up or down.

The things that weren't clear to me from reading the various documents and posts were...

- Each side of the car has an integrated pair of valves. One valve distributes hot air up or down while the other valve distributes the cold air. The hot valves in are linked together as are the cold valves. The hot/cold pairs are each integrated in a single housing.

- A portion of the hot air from each footwell blower is always routed to the side dash vents.

This second sketch shows what I believe is the correct set of connections if the A/C is removed:

Splice a "Y" coupling (91157103900) into each of the hoses that runs from the fresh air blower to the mixing valves. Run the second outlet of the "Y" to the two open hoses left after you remove the "T" union that connects the AC evaporator/blower to the dash vents. Mercifully, all of these connections are on the front side of the bulkhead.

tubwreck · 06-12-2005, 12:49 PM

Just (almost) finished this little project! I attempted to order the Y-ducts suggested by RallyJon (91157103900) but my friendly parts guy suggested 91157103901 as the correct part for my year car ('88).

It took about 3 weeks for the parts to show up, so I assume that they came from Germany. It was pretty easy to get the left side piece installed:

But I could not figure out a way to get the ride side to connect to both the center vent and the right-side dash vent. I probably need another part, but I haven't figured out which part number it is.

It is a very nice improvement to have the fresh air from outside the car now coming out the vents on the dash!

I also removed the switches from the console (let me tell you, they do not slide easily apart as suggested in Bentley), again a nice improvement:

Finally, of course, the nicest part from a service point of view:

I found this change very satisfying, even though it wasn't possible to make the car "just like a factory A/C-delete car". (There are too many big holes in the tub for that.)

Brother · 06-12-2005, 01:33 PM

While you were in there did you see how the heater hoses connect from the mixer or heater boxes to the pipes that take it to the defroster duct. My paper/foil hoses are ripped up in the driver's footwell and hot air blows out here instead of up into the defroster.

tubwreck · 06-12-2005, 01:51 PM

If you look at the _second_ picture in my post, the brown hose on the left side (coming up through the bulkhead) is the ouput from the footwell blower. At the very top of that same picture, you can see a brown hose exiting the mixing valve. That is the hose to the defroster vent.

Hope that helps.