924Board.org

[shorty99]

I've got the strangest problem: no (hot) air comes out of my defrost vents!

Somehow, air always comes out of the side dash vents (the ones directed towards the inside of the car), but never out of the top of the dash. I checked the cable connecting the slider that controls the air going upwards or downwards, and it looks like that's still connected. When i stick my hand inside the heating openings near my feet and move the slider i can feel a large valve move open or shut. Air will come out of there as well, when the slider is in the downward position.

The hot/cold slide works fine.

The fan blows like mad, at least it sounds like that, but nothing ever comes out of those top vents.

It drives me crazy, because driving my car with my head out of the window becomes a little uncomfortable after a while... When the windshield is frosted or steamed up there's nothing else i can do.

Who can help me? Thanks a lot !

I've got an '81 regular european 924. I've checked the forum but couldn't find an answer to my specific problem, the best tip i could find was to just shut the side vents, see if that helps. Excuse my sometimes crappy english.

[Smoothie]

Well, closing the front and side dash vents and setting the slider that controls airflow between foot area/defrost to defrost - that should leave you with air blowing out the defrost. If not, all I can think of is one or both of two things... Either some mices got in and built a nest in that passage that defrost air should blow through and/or one or more of the large hoses that carry air to the front & side vents got disconnected behind the dash, letting air blow behind the dash when the front & side vents are closed. I'd check out the situation further with a piece of hanger wire fed down through the defrost vent/s. Use the thinnest hanger wire you can find - (it'll be more flexible) and bend the end into a j shape to help grab stuff and be carefull not to damage the heater core by poking down too far.
_________________
"..it's made in Germany. You know the Germans always make good stuff."


'82 924T, US version, dark green metallic, 5 speed Audi 016G gearbox

[Mike924]

Hey, Shortie, your English is just fine.

You might like to check that the vents in the top of the dash are clear. The 'thing' that directs the air to them is made of a kind of cardboard, which on my car was distorted through age/heat/time so most of the air was being blown under the dash top and not through the holes on to the windscreen/shield .

If you look down into the holes through the windscreen (from outside the car) you can see if the vents are obstructed.

If they're blocked, it's difficult to get to but you could start by removing the speaker grille in the centre of the dash. Gently bend the 'card' into shape. Be careful as it tears rather easily. I know!
_________________
1985 Porsche 924 'Lux', Kalahari Beige (my ex)
1993 Porsche 968 Coupe, Midnight Blue, 6 spd

'There is no substitute for a little grease under your fingernails.' - Chrenan, 924board.org

[shorty99]

Thanks for the answers !

I hadn't discovered yet that putting the side-vents in the DEF position helped. When i do that, a weak stream of air start coming out of the defrost vents !

I'm gonna check for blockages and check if those air hoses to the side vents inside the dash leak a lot.

How strong should that airflow be ? Hardly noticable or a really strong blow?

[Mike924]

[shorty99]

It really pisses me off !

I just opened the dash, checked those hoses leading to the side vents, they're firmly in place. When the side-vent's slider is all the way down, a fairly strong breeze comes out of them, but when i put it in the 'DEF' position, nothing comes out of the top.

The only thing i can think of is that there's a clog somewhere between the very top and the place where those hoses are attached.

I picture the heating shaft somewhat like this:



Is it really this simple or is it more complicated ?

I looked inside those topvents from outside, with a flashlight, but i cant see anything that shouldn't be there (like that nest of mice).

How deep should i poke in those holes ? about 1 ft. or so ?

[Smoothie]

CMXXXI had a nice picture of the heater unit here - http://www.924board.org/viewtopic.php?t=13312 , but that pic isn't loading currently .

Basically, you have the air intake there outside, between the windsheild and engine compartment. One of the slider controls opens-closes the flap there above the fan and also controls the fan speed. The fan blows down into a box. The passages to the front & side dash vents come directly from this box area of unheated air (your front & side dash vents don't provide heated air). At the bottom of the box is the heater core - air goes through the heater core into a passage that goes down, then up to the defrost vents. Another slider controls the flap that directs air either out the bottom or up to the windsheild. So - for bottom heat and/or defrost, you have to close the front & side dash vents so all air gets directed through the heater core to be blown out the bottom and/or the top defrost vents.
Probably not a big danger of damaging the heater core with a wire from the defrost vents because that passage goes down, then back, then up before it gets to the core, so you should be able to just feed the wire in until it won't go any further. My guess would be something like 1' to 1.5'.
_________________
"..it's made in Germany. You know the Germans always make good stuff."


'82 924T, US version, dark green metallic, 5 speed Audi 016G gearbox

[shorty99]

Strange... I'm pretty sure hot air does come out of the side vents.

Maybe that shutter all the way at the bottom has something wrong with it. But, like i said in the first post, i can definatly feel something BIG moving about 'round there when i stick my hand inside the bottom vents and move the slider.

I've got the Haynes manual at home and i'm pretty sure there's a nice diagram in there. I just haven't got it with me right now. Looks like i'm driving home with my head out of the window...

[Smoothie]

There were two heater designs used in the 924. They changed to the later version sometime in '82, so as far as I know you should have the earlier design - the controls for it consist of 3 full width sliders with one of the sliders controlling the fan. The later design has 2 half length sliders above, one full width slider below, and a rotary switch for fan control to the left. The early design is supposed to be incapable of blowing heated air through the front & side dash vents, but the later design is capable of doing it.
Which do you have - the early or later design?
_________________
"..it's made in Germany. You know the Germans always make good stuff."


'82 924T, US version, dark green metallic, 5 speed Audi 016G gearbox

[Smoothie]

With another look at PET -
I'm seeing something changed in '81. No way to tell from the diagram what effect it had on the operation, but I imagine it could possibly account for heated air coming out the front and/or side dash vents with the earlier version heater. The part is called "air mixing chamber" and 924NA's starting with vin #92BN451918 in '81 got it.
_________________
"..it's made in Germany. You know the Germans always make good stuff."


'82 924T, US version, dark green metallic, 5 speed Audi 016G gearbox

[shorty99]

Well, i got home safely, but not because the defrosting worked.

It really blows my mind. I've got 3 large handles, the lower one is supposed to direct the airflow either up or down.

When in the 'up' position, hot air blows out of the side vents, when i close those (put them in the DEF position), air comes out nowhere.

I've got 3 large handles, the lower one is supposed to direct the airflow either up or down.

It seems impossible but it really is like this. After driving a while, hot air comes out of the defrosting vents, but it's more like it's hovering or drifting (don't know the right word) upwards and is therefore coming out of the top, definitly NOT because it's blown out.

Did you say there are 2 flaps? one down below, to direct the air either down or up and another flap above the fan ? How can i reach that second one ?

is this located in the 'r2d2' thing that sits outside, directly under the windshield ? Thar r2d2 thingie looks extremly difficult to open up, since it's partially located directly underneath the windshield, blocking acces to it.

The Haynes manual doesn't have a picture or drawing of the part that troubles me in it.

Any good tips would make me very happy, since driving a car with a non-see-through windshield absolutely sucks.

[Smoothie]

Yes, the other flap is inside R2D2's head and should be visible through the screen from the engine compartment. It's apparently operating as it should though, since you do get air blowing out at most settings. Did you go fishing with the wire yet? -And what about the warped cardboard scenario - any possibility that that's the problem?
_________________
"..it's made in Germany. You know the Germans always make good stuff."


'82 924T, US version, dark green metallic, 5 speed Audi 016G gearbox

[shorty99]

I went fishing, but the wire goes in smoothly, i've tried about 1 ft. or so. No mice came out.

When i take off the dash, all i see is a black plastic shaft, not cardboard. It goes straight up to the funnel-like top part, which is kinda cardboard-like. The funnel part is firmly in place, and as far as i can tell no air is leaking anywehere near the connection point between plastic and cardboard.

The air that comes out of the side vents is a good gust, but it's not all that strong. Hence the r2d2 question.

I can't stand this: the way i picture it, we're talking about a shaft, you blow in one end, but nothing comes out on the other end. Without there being any noticable blockings. Yet it makes driving my beloved car impossible.

[924guy]

the early "comfort" system isnt very effective, one of the down sides of these cars..but it should at least be enough to get your window defrosted..its sound like your only getting ambient heat on the window side, and i think your on the right track in looking for a faulty air diverter flap..something in that box isnt moving correctly.. its a pain, but you may have to pull the "big" airbox itself..if i recall its built in two pieces and can be split in half for access.. but to get to it, dash has comeout along with a bunch of other things in the way..

the quick fix is to just pick up a couple small 12v high speed fans,the more the better, like from a computer, wire them in series with a cigar lighter plug for power and build a small enclosure for them, that allows you to sit them over your defrost ducts so they draw out the hot air and blow it on your window, doesnt take much but the fans, some epoxy, anmd a peice of cardboard to make a "fan tray" from ...not pretty, but itll work, and its safer than driving without any defrost action at all..
_________________
Eric
78 924
82 931 SE "smokey"
99' VehiCross
Y2K Honda Insight
http://www.cardomain.com/id/924Guy
Performance by Pasha

[shorty99]

I guess building that alternative fanning system will take me probably as much time as taking apart the dash.

The first thing i'm going to do tomorrow is 'fish' the shaft again, with a really long piece of ironwire this time, and if that doesn't help i'm afraid i have to take the dash apart to see if that big shutter at the bottom is working properly.

The way i understand it from all you guys' answers is that the shaft basicly comes down to this :



right ?

the blackish thingy in the lower left is that 'flap' or 'shutter' regulating air going either up or down.

If this is true, i'm going to thoroughly fish the DEFvents for a clog, and if that doesn't help, there's nothinh i can do but take the entire dash apart to reach the flap at the bottom.

looking forward to that ! (not)