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

Ok, so when I pull up the red floor levers I get some air at my feet.
But, if I turn the dial to "3", I should be able to hear a 2nd fan/blower down right at my feet, right?

For reference, the part number for these footwell blowers is
Left-91162404302
Right-91162404402

First, I verified the 3 fuses in the engine compartment wing nut panel were intact.

I then removed the driver's carpet kick panel,
and saw the footwell blower's inline 15A fuse was blown.

I replaced it with a 10A fuse.
Ignition key in position 2.
Heat lever pulled up (Engine blower now running)
I turned the dial to 3, and the 10A fuse blew instantly, with a spark!
Blower motor never spun.
Ok, that might explain the 15A fuse?

I then put in a 15A fuse, and again tried "3" on the dial.
Nothing. Motor still dead.
Fuse got real hot within a few seconds. I turned the dial off.
I thought I could see a wisp of smoke.

Do you think the blower motor is stuck frozen?
Would that cause the behavior observed?
What is the next step in diagnosing this?

Is it easy to remove the footwell blower and try to get it unstuck?
Would the dead footwell blower also explain why I am not really getting heat in the windshield or the side vents?

You should get some heat through the upper dash vents, no matter what. Your engine cooling fan is the primary source of airflow. Some of the air for cooling the motor is bled off into ducts that supply the heat exchangers with air. The additional blower in the engine compartment and the footwell blowers are there to add airflow at low engine speeds. You can heat a 911 without having either of them.

Your footwell blowers are toast. You might remove them and try to resurrect them, as they are expensive to replace. Do a search for the info on how. Don't ever use a larger fuse than what is suggested, the last thing you want to do is fry the wiring and other parts of the system.

Take another look at the upper dash vent heat output while driving (not the face level vents, or the ones at the side, just the ones at the base of the windshield). Keep the engine around 3,000 rpm, and make sure the fresh air side of things is shut off completely. Is there NO heat output there, or just a WEAK output?

JR

Thanks for your help on this one, Java.
I now have a much better understanding of the heater system.

In my case, the blower motor was just stuck.
I was able to remove it and break it free.

Now, it's obvious to me how to know your footwell blowers are dead.
You'd hear them spinning down near your feet very clearly once you turned the round dial.
I think the footwell blower sends air up to the windshield vents and the side vents, which would explain why it was so weak.

The booster fans just add output. Plenty of 911s get along just fine without them. Your car should have far more than "zero" output without them running.


JR

Yea, without the footwell blowers, air was coming out, just not with much force.
It was usable, but I am enjoying troubleshooting the footwells.
Wow, when they work, it's a massive difference.

Tonight, I removed my passenger side blower ...It was also dead.
Compared to the driver's side, the passenger motor squirrel cage was harder to spin.
So, I tried to lube the squirrel cage, and it spun a little more freely.
I never opened the motor. Just lubed the plastic contact points.
Now, the passenger footwell blower motor works....but inconsistently.

I used my multimeter to test the voltage at 0,1,2,3.
I verified the passenger motor is getting low voltage even at 0/1, but not spinning. It spins only on 2 or 3.
This must be that hack they introduced to automatically have the fan spinning when heat was on.
So, the motor is not fully working as it should.

Is it worth trying to open the motor and clean and lube it?
Anyone know how this is done?

So here's a topical related question - are there any shared circuits for the footwell and engine compartment blowers on an '84? In other words, is there any single point of failure that could kill all three blowers?

Here's the deal - I know for a fact that the engine compartment blower and at least one of the footwell blowers was working when I drove the car last week. All 3 speeds worked for the footwell blowers, and I heard the engine compartment blower running when I turned on the ignition (engine still off). Tonight on my way home from work, no blowers at all. Hard to keep the windshield defogged in stop and go traffic.

I've checked the obvious fuses, all seem fine. Haven't had time for systematic troubleshooting yet.

Worse, the wiring diagram in my Bentley doesn't seem to be accurate, seems to assume that all '84s have climate control. (Not true in my car for sure, maybe wasn't even offered in '84?)

Any hints on a common failure point to check? If not, this weekend I'll have to start by jumpering the blowers themselves (make sure they aren't seized) and working backwards from there.

If the engine compartment cabin heat blower does not run then the footwell blowers are disabled. The cabin heat blower control module "monitors" the electrical current flow of the cabin heat blower motor and if it isn't above a certain level the footwell blower power circuit is opened.

Direct wire the cabin heat blower to see if it works.

Perfect. That's the piece I was missing, it makes sense. I couldn't believe that all 3 blowers "just happened" to die at the same time. I'll start at the engine compartment unit.

I have seen reports that seem to indicate that at idle and with a low battery the engine blower does not "draw" enough current flow to close the footwell blower circuit, raise the RPM a bit, footwell blowers run.

Once the DIY solutions I have seem is to bypass the "monitor" reed relay in the cabin heater control module...

NOT a good idea since that might/would result in the footwell blowers drawing in exhaust fumes from under the car.

I'm please enough with how the system worked before the failure. I see no reason to modify or backdate it - I just want it to work.

So, what's the next step?
Applying direct current to the engine blower motor?

This thread has links to the enture $350 assembly and just the $175 internal motor assembly. (ouch)
http://forums.pelicanparts.com/porsche-911-technical-forum/727692-engine-compartment-heater-blower-motor-88-3-2-a.html

This thread talks about the heater blower relay
http://forums.pelicanparts.com/porsche-911-technical-forum/236844-heater-blower-relay-84-carrera.html

Yes, indeed. Might get to that tonight, but maybe not until Saturday.

But wait...there's more...

Here you go...more information about the heater system than anyone should have to wade through. If you have nothing better to do this weekend most all of your questions are answered in these posts. Even some you haven't asked yet. Be aware that some discussions were a journey of discovery, so read carefully and completely to get the entire picture:)

http://forums.pelicanparts.com/porsche-911-technical-forum/388445-carrera-removing-engine-compartment-heater-blower.html

http://forums.pelicanparts.com/porsche-911-technical-forum/97297-carrera-replacement-heater-blower-long.html

http://forums.pelicanparts.com/porsche-911-technical-forum/258473-help-does-anyone-understand-footwell-blower-circuit.html

Good luck...

Checked power to engine compartment blower, 12v. Good.

Pulled blower from car, disassembled. Brushes are totally worn out. One wore far enough that the copper braid lead came loose. Motor dead.

Might be worth looking for replacement brushes that would fit, but don't know how easy those are to find these days. Would be far more affordable than a replacement motor. But if it takes a new motor to fix it, so be it.

Thanks to all for the info and support on this.

Maybe worth a look....

Factory Air Blower Motor Wheel - 35214 - Page:2 - Detroit Motor Parts

Find OEM Specialty Blowers and other Fans & HVAC Equipment at Zoro

Blowers / Jabsco Blowers / Fans & Blowers / Marine Products / Xylem JabscoShop - Jabsco & Rule Pumps and more - from the experts

Your local electric motor re builder should be able to get brushes for you for $20 or less.

Sometimes you can find something close that is a little bigger and whittle them down.

Get a can of electrical contact cleaner and clean everything. 1000 grit paper
For armature and a dab of lithium grease for bushings if they are just dry and not
Worn out.

Keep us posted.

Did a little digging, and decided that in addition to the brushes being shot, the bearings are questionable at best. And while they too could be replaced, when you add those bits to the desire to have a working defroster system sooner than later (cool and damp now here in Western Oregon, and I drive the car regularly, even in the rain), I went ahead and ordered a new motor (the aftermarket replacement) from our host. I'll keep the original for possible parts use later.

Will also be looking at the footwell and ventilation blower motors later, as I suspect they may not be much better inside. Time for a little preventative maintenance.

The link in the OP may be helpful in the footwell blower area.
Good chance they are just stuck with a blown fuse.

Dumb question, after reading the posts. It isn't clear, are the footwell blowers just for heat or fresh air as well?

EDIT: Went and checked them out. Appears they only come on with the heater, no AC or fresh air. And my passenger footwell blower isn't working. Eh, it will be on the bottom of the list to do. It is Texas and I hardly ever have a passenger in the car. :)