Heater controls 101. Dead footwell blowers? Windshield vent not blowing air.
 

UPDATE: My footwell blowers were dead (stuck), causing little air to reach to the side cent and windshield vents.
If there isn't serious amounts of blowing air coming from the bottom or top vents, then your foootwell blowers are dead.

Here is how to fix your stuck footwell heater blowers.
http://forums.pelicanparts.com/porsche-911-technical-forum/835822-round-heater-dial-should-create-blast-air-heater-blowers-if-not-read.html

Summary of HVAC controls:
There are 3 rows of levers on the dash.
The top row controls fresh air only. Top left lever controls amount of fresh air. Top right controls fan speed.
The middle row directs fresh air up or down.
The bottom row directs HEAT air up or down.

The floor levers control heat.
Pull up on the lever, and it turns on the blower motor mounted on the engine itself.
The lever also control the butterfly air mixing valves underneath the car.

The round console dial controls the footwell blower speed. These may be dead or stuck on your car.
When you turn the red dial, you should hear fans down at your feet at the kick panel.

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I was hoping not to start a thread, but I think I need some direct feedback.

The problem with whole thing is that I only ever try the heater controls while I am busy driving.
Not a great time to learn something new. Maybe I should test this while idling in my driveway?

First, I'll add this here for reference.
http://members.rennlist.com/imcarthu...ercontrols.jpg

On the dash controls, I use "fresh air fan speed" (Top row, right lever) to get the fans blowing.
While I hear sound, I don't really feel air coming out from anywhere. Not the vents, not the dash, not the footwell.
Where is the air going? Do I HAVE to have these fans turned on to get heat? Or are they only for mixing in outside air?
http://i57.tinypic.com/aw8bqu.jpg

The 2 red levers on the floor. When I pull up, I feel hot air at my feet.
This seems the only way to get heat into the cabin.
These seem to be the only controls that do anything.
http://i62.tinypic.com/34har9f.jpg

On the floor console, I also have a dial that can be set to 0,1,2, or 3. The heat works from the lever regardless of what this dial is set for. What is this dial for? It doesn't appear to do anything.
http://i60.tinypic.com/34hxppl.jpg

I am not sure my windshield vents are working. There is no obvious rush of air coming from dashboard vents near the glass, regardless of settings.
If I have the red dashboard lever set to "up arrow", and I pull up on the red floor levers, I should have a ton of hot air coming out at the windshield vents? What if I don't?
What would be the proper test? I put the 2 dashboard levers from row 2 (black) and row 3 (red) to the right side (up arrow), and I'm not really feeling any real air coming out at the windshield.

When you figure it out, let me know! The last owner lived in NC and never touched the levers.

Right now, I have it arranged so that pulling the red levers on the floor makes heat on the windshield, and turning on the fan makes cool air on the windshield. That's good enough to drive, but I can't make it do anything else. It would be nice to be warm on cold days with the roof off.

Probably the entire set of cables and flappers needs to come out, get lubricated, and be carefully reinstalled. Some other time...

You must move both top black levers to the right in unison to get air into the cabin, just moving the right one over while leaving the left one at its far left position will turn on the fan but keep the air valves closed thus no air.

As it turns out, one of my flapper box cables is broken, and I need to get in there and replace the cables. Yes, not cable, but cables. It doesn't make sense to replace one but not the other. I'd like to do the whole mess in stainless steel, and lubricate it in the guide with BOEShield.

But that would require me to know the diameter and length of the cable. :)

http://forums.pelicanparts.com/uploa...1411686448.jpg

This was uploaded by another pelican, but I found it helpful.
Hope it helps
Kurt

Notice that what is underlined in yellow contradicts the lever positions in the red box. The picture is wrong, it should show both levers to the full right so the fresh air vents open and the blower is in max.

While you are at it. Confirm that your footwell blowers are fused. Porsche didn't fuse them from the factory on 86s. My set up is just like yours. My rotary center knob can be a little finicky. A little wiggle sometimes is all it takes to get it to work. It should light up when on (with levers up). -J

Not exactly, it depends on the car. A ROW car without A/C. for example, may have a different arrangement than what you think. In that case, what you see written is correct and the center vents they refer to are the ones in the middle of a dash from 1977-on. With the upper lever to the left and the dash vents open, you will get airflow.

The mistake people often make is that they think of these cars as being all the same, when in fact there were a half dozen different variations of the HVAC plumbing. It's usually safe to read the owner's manual of YOUR car and do what it says.

JR

No, He is correct the pic is wrong .. I have a ROW car without AC , yes you will get airflow by opening the centre vent .. but to get MAXIMUM air flow you open the centre vents on the dash and also the fresh air vents by moving the upper lever to the right ..

I checked my manual. Solved all my questions.
Of course, I don't have A/C, so I have that going for me!

Take it one step further and try to understand what their intent was. In Europe, they tend to not run around with the windows open as much as we do in the US. The ventilation that you feel from the upper dash vents is next to nothing, I don't care how open they are. If you want to feel cool air, you use the center dash vents. If you also have the dash top vents open, the ventilation that you feel from the center dash vents is less.

I've actually added additional butterflies into the fresh air blower housings of a couple ROW cars I've owned, to allow me to completely shut off all outside airflow without having to rely on the louvers in the center dash vents, whic leak a little air, even when closed.

Maybe it a semantics issue. The bottom line is that people need to understand what's on the other end of each of the cables and how their system is plumbed. It's not hard, if you think about it for a few minutes. It's also not always helpful to post a diagram for one layout when the question is about another layout.

JR

Well i think we all agree that 911 HVAC controls are Hitlers revenge for WW2 !!

I think they work great. Only car other than some older BMW's that give you complete control over what you do.

JR

They should have kept the front opening vent wings.
Yeah, javadog, the best is to follow the cables and understand what they do, l had the complete blower and housing out to clean and replace the blower and it answered a lot of questions.
BMW is not the only one that gives driver all kinds of combination of airflow, my Peugeot has got a great HVAC system.

I verified that the floor levers do 2 things.
The work the flapper box under the car, and are connected to a blower motor.
So, the red floor levers are the heat on/off switch, not just duct controls.
This heat works independently of the top row dash levers for fresh air, which can be in the off position (both left)
Want heat? Pull up the floor lever.

When I push both top row dash levers (fresh air) to the right, I get a big surge of fresh air blowing, and it can be directed to the footwell or the windshield, using the row 2 dash lever.
However, it didn't feel like I was able to direct heat up the the windshield. I pulled up the floor lever, and then pushed the red dash lever to "up". I hear the blower, but don't feel where the air is blowing.
When the red lever is pulled left to "down", heat goes to the footwell. How do I look into this further?

I did not verify what the round dial that goes from 0-3 does.

The round dial is a control for your booster fans. 0= off, 3= max, etc.

If you don't get heat to the windshield when the bottom lever is attempting to direct it there, go in the trunk and have a look at the cables on the air distribution boxes.

JR

Java,

I pulled the floor lever up to turn on the heater fan. Fan blows like it's on a low setting.
Then, I changed the round dial from there ....It did not seem to have any effect on air speed.
You're saying another booster or blower fan should be triggered from the round dial?

I looked under the curved cardboard cover. All the linkages appear intact and working.
The fresh air mix lever (top row, left lever) controls the center fresh air blower linkage.
The cold air lever (row 2) controls the left and right side box, front linkage
The hot air lever (row 3) controls the left and right side box, rear linkage (out of view)
Beyond that, I'm not really sure how to troubleshoot the heat routing to the windshield.

The dial should cause the heat output to increase. It's likely that your booster fans are not working.

Look under the car in front of the rear wheels, up high, to see if when the red levers pull the cables, the cables actually move the valve in the boxes. Then, look to see if there are hoses connecting to the heat exchangers (on each end of the heat exchangers).

Since you feel hot air at your feet, at least one side ought to be working, at least partially. If you verify that you can get a normal amount of heat at the floor, but nothing goes to the windshield when you move the lower dash lever, then the problem is inside the distribution boxes, or a hose has come loose in the trunk.

JR

Yes, the floor levers work properly.
When pulled up, it starts a motor, and hot air is delivered to my feet.

Yes, both floor levers correctly open and close their respective heat exchanger doors.
http://members.rennlist.com/imcarthur/HE-heat-valve.jpg

I didn't see any loose hoses in the trunk behind the curved cardboard barrier.
Where are the booster fans?

Booster fans are behind the kick panels in either footwell.

JR