911 heater settings--epitome of poor design

[ljonespwc]

I can't take it anymore! I've tried to solve my problem by reading the owners manual, by staring at the diagram in my glove box, and by asking my knowledgeable local wrench.


It's getting warm out here in British Columbia, and my 1988 911 CS has no A/C. So I've been trying to configure the heater sliders to keep my interior cool, but to no avail. I know the topmost of the 3 sliders operate the fresh air fan, but no matter how I adjust the lower 2 sliders, I either feel heat blowing in the footwell, or from the base of the windshield.


How can I stop the flow of warm air completely? I can handle no back seat, manual window rollers, and virtually no sound proofing, but hot air blowing on a warm day is too much!


Any pointers for a relatively new P-car owner? Kind regards, Lance.

[Superman]

The lower (red) knob on the dash just send the warm air to the windshield or the floor. Turning the hot air on or off is done with the two (red) levers between the seats (I hope you have manual levers here). When you push them down, the heater boxes should be opened completely. They are under the car, near the engine, between the rear wheels. You have to get your face under the car to see them I think.

If heat is coming into your cabin, then these heater boxes are not opening all the way. They must open to allow the hot air to escape the heater system into the outside air.

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'83 SC

[Rod Walter]

Just to follow up on Superman's comments. If both red levers are all the way to the floor and you still feel some warm air bleeding into the cabin, the heater "flapper boxes" can look like they are exhausting the heat to the outside but they are not. I know because I had this problem.

The cables from the red handles between the front seats control a rotating disk on the heater box, not unlike the arrangement on some spice containers. Pushing the red handles down rotates the disk to expose holes in the heater box so that the hot air leaves the system before entering the cabin. But the disk is also connected to an internal plate that you cannot see inside the box. This plate must close all the way or you will have a constant source of heat in the cabin. In my case the holes were fully exposed but the plate didn't close all the way.

Fortunately, the fix is easy. Simply adjust the cable connection at the box so that the internal flap closes. Put both red handles between the front seats all the way down. Loosen the nuts clamping the cables at the heater box disks. Counterhold the bolt heads so that you don't twist the cables. Now, with the clamping nut loose, make sure that you can feel the flap positively closing and retighten the clamping nut with the flap closed. This is easier, by the way, if the rear tires are off to give you some working room.

Good luck!

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Rod Walter
'88 911 coupe

[Jorgeman]

Lance--my 86 Targa doesn't have the two levers mentioned above because the system is "supposed" to be automatic. The heater boxes are opened and closed via a servo motor inside the console behind the emergency brake and respond to the 10 position switch sitting on top of that console. A common failure is that the rod connecting the servo motor to the bellcrank that operates the heater box valves loses one end or the other leaving the heater boxes part way open. Easy enough to replace if you follow the instructions in the Bentley manual. You can disregard the above if you have the manual levers and follow previous instructions on assuring their closure. Good Luck

George 86T

[Nickshu]

The automatic heater control still uses the same heater boxes/connections, but they converge into 1 cable/lever rather than 2 on the manual control. So in addition to what George said, you could still have the same cable adjustment problem that others described.

I had this problem. The boxes stayed slightly closed causing heat to be passed to the passenger compartment. This really sucks when you are in pants and long sleeves with a helmet on in 90 degree weather (happened at my last DE). A simple adjustment of the locknut where the cable attaches to the boxes solved the problem. If a cable breaks the box will default open (because of a spring), so you probably don't have that.

The box looks exactly like the adjustable vent holes on the cover of a Weber charcoal grill. Jack the rear of the car and look just inboard and in front of the rear wheels. You'll see 'em.

Nick.

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_ _ __ _ _
Nick Shumaker
1982 911SC Coupe
nickshu@yahoo.com
PCA -- Rocky Mtn. Region


[This message has been edited by Nickshu (edited 06-17-2001).]

[Rod Walter]

Thanks, Nick, for the Weber grill analogy - you're right, that's exactly what they look like All I could think of were the lids of parmesan cheese jars and those little spices.

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Rod Walter
'88 911 coupe

[ljonespwc]

I have the levers, thanks.

That's fantastic information, guys. I would never have though of those things myself. The second best thing about owning a Porsche is participating in this forum--makes it almost OK when something goes wrong (hopefully not too expensive though). Kinds regards, Lance.

[89911]

Try my method: Move all the levers in every direction while driving and feeling for some cold airflow from the vents. Upon discovering there dissapointing function, wind down the windows and open the sunroof.

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8 9 9 1 1, The last of the line.

[ljonespwc]

OK 89911, I would if I could. First of all, I've tried your method countless times, and have almost put myself into a ditch as many times as I've attempted it. Problem is, I don't have a sunroof, and my windows are manual--try rolling down a passenger side window while driving. It ain't pretty.

[89911]

The basic probem with 911 design is that the engine and HVAC systems are in the BACK, and are going against the natural airflow that a fron engine car has. My car has no inlets that let air coming from the front directly into the car. It is all redirected stale air from the back. It never feels cool, despite the outdoor temperature. I was somewhat serious in saying to open the windows, at least for fresh cool air.

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8 9 9 1 1, The last of the line.

[Superman]

My system works just great. Levers down, heat off. Levers up, it's a 140 mph convection oven. A/C blows cold air. Vents make fresh air. Volumes are modest though, and if the system is broken or misadjusted, it works poorly.

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'83 SC