Avoiding the shop...another flapper box question

nealf2002 · 10-12-2009, 06:07 AM

OK, so I can feel under the car and access the flapper boxes, even prior to jacking the car up. If I disconnect the springs going to the flaps, can I close the boxes and obtain some heat? Keep in mind, when I bought the car back in March, '09, I stupidly yanked on the red lever between the seats and must have snapped the cable going to the boxes. I do have the auto/electronic (whatever) heat in the car, a '82 SC RoW.

Please bear with me as I want some sort of heat and dread having to take the car to the shop to get sorted...my old BMW's are much easier to sort...

Thanks.

nf
'82 SC Row
'72 2002 Tii
'70 2800CS

chamilun · 10-12-2009, 06:46 AM

yes, you can, but keep in mind youll have constant heat, all the time.

brads911sc · brads911sc's Garage

******** sells the boxes... you will need to buy the special one for auto heat for one of them. Our host here doesnt sell them. Jack up the car... remove old boxes, install the new boxes. Order a new sleeve if needed (this was NLA when i did mine so I made one). Order the nuts and bolts holding on the cable... these will break if you try to reuse them, order a new cable if broken, order a new set of hoses... You will need to crawl under there twice would be my guess... Its worth the new parts if you really want heat. Will cost you a total of less than $350 if you do it yourself. I did mine.. took me about two-three hours total. Really not that bad of a job...

chamilun · 10-12-2009, 07:35 AM

I had to break my cable, somewhat accidentally, to get the drivers side all the way open. Im now going to try and repair the cable by using another piece of wire and two nuts on either end. Hopefully will work.

I wouldn't remove the spring if possible.

rattlsnak · rattlsnak's Garage

If you have auto heat, chances are you simply popped the rod off the actuating arm. You can pull the four bolts off the cover housing behind the brake handle and resecure the rod and it should be ok. With this system, if you manually pull the red lever up, you are pulling against the motor and it will literally take 2 minutes to pull it all the way up. If you try to do it faster, it will pop off.

Gunter · Gunter's Garage

I had the automatic heat control in my SC and disconnected it as follows:

Open the control box between the seats, disconnect the small rod that actuates the lever. Now the flapper boxes are manual.
Because the return springs are very strong, I replaced them with weaker ones so they don't pull back too hard on the manual lever.
I lubed the cables from both ends with light oil.

nealf2002 · 10-12-2009, 09:36 AM

I will take this all into consideration and let the forum know how I make out...

One question though, when someone said, heat on all the time if I manually close the flapper boxes, does that mean heat pouring into the cockpit even if the fan control is turned off?

On my old BMW 2002, the heater valve was inoperable and I installed one from an old VW, with a "winter/summer" type of sliding lever which would either let coolant flow or not. It was located under the hood, but I couldn't care less. So what I couldn't control from behind the wheel.

I am not so much concerned with heat all the time as I am facing the prospect of not being able to drive the car in the cold because of no heat.

Thanks again.

dan79brooklyn · 10-12-2009, 12:46 PM

You WILL get plenty of heat even without the fan on. Like burn your feet hot.
The pre SC 911s did not have the engine bay fan and only used the pressure from the engine fan to push through hot air. So there is plenty of heat forced through at anything above idle.
If you just close the boxes a bit you should be able to find a comfortable temperature for the wintertime.

kidrock · 10-12-2009, 06:30 PM

+1, the boxes do not need to be fully closed in order to provide adequate heat. The Porsche is not only a great car design, it also doubles as a rolling heater.

nealf2002 · 10-13-2009, 08:13 AM

So many of you have concluded, I need to partly shut the flappers and I will have heat! If I take the spring off, and partly close them, what will keep them closed?

Thanks again.

Gunter · Gunter's Garage

To be clear:

The springs close the valves, diverting the heat to the outside.

When you move the lever, you're working against the springs allowing heat into the cabin.
Removing the springs will result in easier opening of the valves but may not close them when moving the lever.

Provided that the heater ducts are good and connected, plus the heater boxes and valves not rusted out, there should be heat.

Gogar · 10-13-2009, 09:18 AM

Neal,

I'd suggest if you can get under there there's probably two points where you can zip-tie the flapper closed, or partially closed. Don't mess with the spring if you don't have to.

If you're afraid the zip-tie will melt, maybe use some 18-gauge steel wire, which coincidentally is the same gauge of wire you will need to replace the broken cable in the sheaths up to the controls in the tunnel. You don't need new complete cables, just the steel wire inside the cable.

nealf2002 · 10-14-2009, 03:48 AM

Ok so was under the car, and the flapper boxes need some freeing up via PB Blaster...so I am working on it. I still don't understand what opens and closes the valve in the flapper? With the auto heat control, is it turning the rotary dial? How about the temp slider on the dash? I could not see what would move in the cockpit b/c I was under the car. All help appreciated!
p.s. Cold here this morning in Philadelphia, 39 degrees on my temp gauge currently...

Gogar · 05:21 AM

The flapper box mechanism all works as one motion. The cable that's coming from the tunnel on each side of the trans pulls/pushes on the flapper 'door' to open/close the holes. The parts inside of the flapper box that move you don't really get a chance to look at, unless you take the whole flapper box off the car. Which is usually a PITA.

If your cable coming from the tunnel is actually broken, you should be able (once you free up the flapper doors) to close them by hand and tie them closed.

If the cable is NOT broken, it may be hard to manually close the flappers under the car, unless you unhook the cable from the flapper box. 7mm, don't lose any parts and remember the sequence of bolt/flapper/washer/cable/nut.

I'd say soak 'em with the PB blaster and then after a day or so try to move the controls between the seat again. Someone needs to chime in about how the auto heat works, too.

If your car has an owners manual, maybe check out the auto heat section and make sure you've got a handle on what the controls are supposed to be doing, too.

rootmatt · 10-14-2009, 05:57 AM

What opens and closes the flapper? When you rotate the dial on the auto heat control, you set the required temperature. The interior temperature is sensed by a sensor located above the windscreen near the interior mirror (took me a while to find out what that was). After comparing the set temperature and the interior temperature, a servo motor in the auto heat control winds the control lever (on front of auto heat control box) up and down as required without any input from you.

If this should fail, there is a small screw at the base of the control lever. Removing this screw will disengage the control lever from the auto controller to enable manual control.

The sliders on the dash do not control the amount of hot air. The red one simply diverts the hot air up or down.

Matt

nealf2002 · 10-14-2009, 08:11 AM

I really appreciate it and will take a run at getting some heat again tonight!

nealf2002 · 10-19-2009, 07:08 AM

Was able to go to my buddy's lube shop and get under the car via the pit. We zip tied the flapper boxes some of the way closed and voila, an intense amount of heat...they are in better condition than they appear in the photos, the passenger side was a little bit stuck and a couple of shots of PB Blaster and it freed right up.

I do however, think I may have an issue. I am smelling some exhaust and worried about driving with the windows fully closed.

My question is how could exhaust be entering the flappers? Would there be a leak up near the heat exchangers? If so I did not even look over there while under the car.

All help appreciated.

Thanks,

nf
'82 SC RoW

Gogar · 10-19-2009, 07:19 AM

Quote:

Originally Posted by nealf2002

I do however, think I may have an issue. I am smelling some exhaust and worried about driving with the windows fully closed.

That is called "Porsche ownership"

But no, really, you can check for exhaust leaks around your headers, and header to muffler. In rare instances if your Heat Exchangers are really rusted some stinky air could be getting into the exchanger from the header, but it's really doubtful if you ask me.

If you think about how it works, the fan is sucking air from around the engine onto the engine to cool it; that air by design is going to have some exhaust fumes in it.

the best remedy is to just check your headers/muffler for good seal, and make sure your engine is really clean, especially behind the fan and under the shroud (PITA.)