Pavegeno928

I have posed this question to PCA and am looking for some confirmation from any of you that may be very smart on the HVAC system on my '88 3.2. Even if you are not smart on the system, perhaps you can print this out and try it on your car and let me know what you find.

Question: When the fresh air fan is on (not the A/C Fan or heater fans) is it possible to direct fresh air out of the center vents (again, not refrigerated air or heat)?

My owners manual says on pg 39 under the title 'Center Vents,' "To increase the supply of fresh air to the vents in the center of the dashboard, slide the upper left lever completely to the left, i.e. the fresh air supply to the windshield and the footwells must be closed."

When I turn on the fresh air fan and move the upper left lever on the HVAC panel to the middle, I can direct fresh air to the defrost vents or the footwells depending on the position of the center lever. That is easy enough.

However, when I move the upper left lever to the left with the fan still on, no air comes out of the center vents as the owners manual would lead me to believe.

Can anyone help here? Does anyone get fresh air out of the center vents on the dash with the upper left lever to the left and the fresha ri fan on?

Thanks!!

BMWDavid

On my '89 Carrera I can not get fresh air from the center vents per the above settings. I'm also lead to believe via the owners manual that you can get fresh air from the center vents.

Sorry this is not more informative.

David

imcarthur

See Auto Heat for more detail.

Ian

BMWDavid

Wow! Now I understand in much more detail what is going on. Secret handshake indeed!

Thanks!

David

Pavegeno928

Perfect..thanks...so the center vents do get fresh air only if you don't have A/C installed. That makes sense.

imcarthur

Nothing in the AC/heat equation on a 911 makes sense. It was an afterthought at best.

I can 'see' the retired 911 engineers gathered at a watering hole in Stuttgart laughing & reminiscing about it . . . "Hey, Hans, remember when you suggested to Dr. P that we just slap the AC on top of everything else? Hahha. And he said yes! AC, fresh air & heat that works all at the same time! Haha . . ."

Ian

Jay H

Ian,

That's an outstanding and very acurate graphic you posted!

Jay

JV911

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 Porsches 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 signalling 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 colour) 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 newer Porsches, 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 vapour on the windshield, so no one can see in or out of the car -- sort of like privacy glass.

tone40

air will out come out the center vent if there is no A/C system installed. I don't see anything that suggests that. Fresh air only seems to be directed to the windshield vents or the footwell vents. Can someone clarify this?

Additional question: When the cool air fan is operated (allowing air flow through center vents), is the A/C compressor actuated? Or, does the compressor only actuate when the A/C **** is rotated?

Pavegeno928

If you click on the Auto Heat link in imcarthur's post, you will see the same color graphic showing fresh air coming out of the center vents only when no factory a/c is installed. Hope this helps.

I'd like to know the same...if the A/C temp **** is turned fully counterclockwise, will the AC fan run without actuating the compressor?

Jay H

If I remember correctly from my '86, I would turn the A/C temp **** to the warmest setting (fully counterclockwise?) and then turn the A/C fan **** to on (to whatever speed I wanted) and get just fresh air out of the center vents. The A/C compressor would rarely cycle on and off with that setup. On really hot days, I think I remember the compressor still kicking on and off at times. But on cooler days, it was somewhat of a way to cheat the A/C system and just get fresh air blowing through the center vents verses having the 'penalty' of the A/C compressor coming on.

My current '84's A/C system does not have a belt on the A/C compressor and the wire to the compressor has been disconnected. That allows me to use the A/C blower that blows through the center vents as a nice fresh air blower. Of course in hot climates, this would not be very usefull. But, in moderate WI, it works well in spring and fall.