How does the heating system work for 74-89?
 

Can anyone point me to a doc that explains how the heating system works for the mid-year oil cooled cars? I searched forums but did not find any overview explanations. Thanks in advance,

Paul.

The basic system works like this:

Red tipped levers on the floor between the seats are pulled up, opening the flapper valves on the heat exchangers. This channels warm air into the cabin. The dash controls--typically three rows of levers--uses the bottom red tipped lever to direct the air to the windshield or the foot wells.

Now, there are some variations depending on the year of the car. Some cars have "auto heat" which opens the flappers mentioned above by turning a switch and small servo motors. Some cars have footwell booster fans to force more air out. The dash controls are essentially the same though--top two rows are for fresh, outside air, and the bottom red control for direction of warmed air.

Best to get a driver's manual for your particular car and read up. Failing that, post the exact year and model here, and someone with the exact car will fill you in on the details.

Try the search button on the top right of the Technical page and try search words like "heater" "dash controls".

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This is a commonly asked question, so I thought I would re-post something I wrote up for the old Porsche Email lists before the dawn of the Pelican.

Q: I just bought a 911 and can't figure out how to make the heater work -- or the fresh air either. Can you help me?

A: Sure, I can help you. The ventilation system requires that you operate 4 levers to make it work. 3 of the levers are on the dash, and the other is between the seats -- on newer Pooscheys there are 2 levers between the seats).

The top lever on the dash actually does several different things (remember, it is a fiendish German device, just like the rest of the car). Pushing it to the middle opens the dust ports leading to the windshield (see below for operation of fogging machine and oil mist spray device). Pushing it to the right past the middle also activates the rattling noise-maker device. There are three loudness levels to choose from. Pushing the lever all the way to the left is used to jam the cable so unauthorized personnel cannot operate any of the devices above. The lever also enables the automatic heat exchanger signaling device -- when opening it spews rust particles on the windshield, you should replace the heat exchangers. Also, if opening it causes you to immediately turn blue or purple (not just hair, but skin color) and become unconscious, you (or your estate) should definitely replace the heat exchangers.

The second lever from the top controls the lights on the White House Xmas tree. Move it to the middle to turn on the lights, and all the way to the right to fire 4500 Megatons of Nukes at Iran.

The bottom lever on the dash is used to replace the windshield when it becomes scratched or pitted with rock chips. It also determines how much hot air goes to your feet as opposed to your head. For example, let's say the engine is completely warmed up and the hot air is burning your feet. If it's a cold day, you can flip the lever to the other side and shoot hot air onto the windshield so it cracks and shatters. Then call your insurance company (you do have insurance, don't you?)

The lever between the seats controls the oil mist spray device. When the engine is warmed up, this lever allows you to blow oil mist into the passenger cabin. Using the top dash lever lets you select whether you want the oil mist to coat the inside of the windshield or to just circulate around your feet. On a newer Pooschey, you have 2 levers on the floor between the seats. The left hand lever lets you open the left side vents which are aimed so they burn the feet of the person in the right hand seat, and the right hand lever lets you open the right side vents which are aimed so they burn the feet of the person in the left hand seat. Of course, each lever will also burn just the tops of the feet of the person in the other seat. If you are driving in the rain (or even stopped in the rain after the car has broken down), these levers also let you spray a fog of water vapor on the windshield, so no one can see in or out of the car -- sort of like privacy glass

I think I remember reading that post back in the early '90s on the Porschephile list (Stan Hanks was "moderator"). It was funny then too.

Try these links:
03-01_911_heater
911 Auto Heat
http://forums.pelicanparts.com/porsche-911-technical-forum/438183-911-heat-questions.html
Porsche Club of America, Northeast Region

Yeah, I always loved this pic:

http://members.rennlist.com/imcarthu...ercontrols.jpg

When you figure it out please let the rest of us know!!!

How does the heating system work for 74-89?

Poorly.

Except when it roasts ya'. ;)

Good stuff!

My 85 will roast you for sure even on very cold days. I would say it works great.

Here is a complementary pic of the layout, which I obtained on this forum:

http://forums.pelicanparts.com/uploa...1265247325.jpg

heat
 

great stuff everyone. the mysteries of porsche 911 auto heat diagram is good. i was curious about the servos when i turn my heat on, ie where are they and how do they work. looks like they are the Heat Control Valve...which makes sense to me now as they are connected directly to the console between the seats. my heat works exceedingly well, and the a/c is not bad using a sanden compressor new filter etc. . love the comic review---funny stuff. really appreciate the feedback from everyone.

best, Paul.

i forgot to mention i took the car out in 20 degree weather and it took some time for the heat to finally kick-in, even though the motor had warmed up....when switching on the heat, i could hear the servo motors, but i had to drive 15 mins before the heat came on...i have a feeling the servos were to cold to operate.

which would defeat the purpose of having them as part of the heating system...!:D

You gotta love the design that has no fresh directed at the driver, just non working air conditioning.:rolleyes:

Keep in mind that the system used on a 911 is different from that in a 930; the 911 systems varied from year to year; in a 911 you could have manual or auto heat...

There are at least 6 variations that I can think of. So, don't assume that everything you see above applies to your car...

JR

If I want the creature comfort of a predictable cabin temperature other than hot, hotter and hottest in the colder months, I drive the Audi.

footwell blowers
 

Hi Can you help,
Ive just replaced the fresh air blower motor and this works!!!!:)
The footwell blowers have never worked - if I remove one and add 12V they work fine. does anyone know where they are switched from ?
Please help
Thanks Chris 1986 911 turbo bodied cab:)

The round knob between the seats, by the handbrake.

JR

This explains it well. I can't drive the car when it is colder than 50 degrees because the tires ***** and squeal at me. So the warning that came with the tires is true "these tires won't stick below 50 deg. "