Robert Coats

I've figured out almost every button, **** and switch on my '91 C4, but...

(1) On the A/C panel, there are two small square (snowflake) pushbuttons at the far left side. The bottom one works as I guessed; it engages the compressor, just like many other cars. The TOP one, however, has me wondering. It too, engages the compressor, but it also puts the fan at maximum speed. So, is that all it does? Why do you need it?

(2) When running the A/C, I pressed the recirculate button, just as I would do in other cars, to maximize the cooling air. However, in the C4, I don't detect a difference when I press the recirculate button. I turned everything off, and felt a very small amount of air exiting the vents, then pressed the recirculate button, and the airflow stopped. So, I'm 99% sure the recurculate button is working as it is supposed to, but why don't I get an increased airflow when I press it? I'm thinking it has to do with how fresh/recirculated air is processed in the car, but please enlighten me.

Drew_K

Robert,

(1) I'm not even sure that button turns on the compressor. I never use it, although I guess it's a shortcut to turning the fan level to 4.

(2) My understanding is that the recirculate button doesn't give you MORE air flow. Instead, it controls where the air comes from (outside or inside). On hot days, recirculate should blow cooler air by not using any of the hot outside air.

Robert Coats

The top "snowflake" button seems to work exactly like the bottom one (e.g., turns on compressor) but it also disables the fan speed control and locks the fan on HIGH. Like you said, it seems to be a "shortcut" to get maximum A/C operation.

It seems redundant, if indeed, that is its only function.

Randall G.

Hi Robert,

(1) Without sitting in my car looking at the panel, I believe the upper button is your defroster. Turns on the compressor (dry air), kicks the fans into max speed, and should direct a whole lot of air to the base of your windshield.

(2) Interesting you should mention the recirc. button. About two weeks ago, in anticipation of coming up to where I knew a skunk had been hit, I swapped the ventilation into recirc. mode. As I drove by, I still got a whiff of skunk smell. Made me think something was perhaps wrong with the recirc. mode.

Dug into the owners manual, and learned that the recirculate mode does not completely cut-off outside air. Perhaps that's the reason I still got a whiff of skunk smell? Still .... now that I was listening for it ... I noticed that the air-flow didn't increase when in recirc. mode. So ... it makes me feel better to read that neither Drew or yourself have more air-flow when in recirc. mode.

Anyway, is anyone aware of a way to verify the recirculate mode is operating correctly? I haven't been able to think of one. A "smell-test" is tough to quantify, considering that the recirc. mode does not cut-off outside air completely.

Did your car come with an owners manual? If not, you can buy one from either Performance Products or Tweeks, perhaps others. Around $25, as I remember.

Randall G.

Hi Robert,

Just took a look at my '91. I only have a single (snowflake) button on the left-hand side of the climate control unit. The defrost button is on the right-hand side of the unit.

Sounds like you have an updated unit. As I recall, the replacement unit has two buttons, and the button in question is for "Max Cooling"--automatically puts the ventilation in recirculation mode and runs the fan in max. speed. I agree ... it's a pretty worthless button ....

Suppose it's possible the two-button climate control unit was a mid-year change--I don't know. What's your manufactured date? Mine is 11/05/90. Anybody with a '92 that has a single button on the left-hand side of the unit?

Robert Coats

Not sure when my '91 was built, but it was, according to the maintenence book, "put into service" almost exactly 10 years ago.

I do have the owner's manual, but the illustration and instructions for the A/C only show and mention a large, single "snowflake" button.

I did some testing, and here's what I discovered...like other "funny" things German, I think my C2's ventilation system is like characters on "Hogan's Heros." To wit:

(1) Defrost button = General Burkhalter; loud, commanding, and overrides everything else, no matter what. Blow lots of air, straight up.

(2) Top snowflake button = Col. Clink; tries to be loud, restricts Col. Hogan (see lower snowflake button), but can be overridden by General Burkhalter. However, everybody knows to easily get fast results, just press the top snowflake button.

(3) Bottom snowflake button/fan speed **** = Col. Hogan; smart, does what you need, and works well with other controls

(4) Recirculate button = Sgt. Shultz; doesn't really seem to do much, easily overridden by Col. Clink and General Burkhalter all the time.

(5) Slider Controls = Hogan's men; they do the job just fine, thank-you-very-much, and try very hard, but are usually overridden all the time. They don't really pay much attetion to Sgt. Shultz, either.

Randall G.

Hi Robert,

Like the Hogan's Heroes analogy .

Your manufactured date is on the inside of the driver's side door jamb. Considering that your owner's manual doesn't describe the second snowflake button, I'm guessing the climate control unit has been replaced. Not uncommon.

Those damn slider controls are completely non-intuitive. At least I think they are. The only setting I can remember--after owning the car for 9 years--is both sliders all the way to the left cuts off air to your feet. I know this because it keeps the A/C from chilling take-out food.

Jay H

As Randall states:

"Those damn slider controls are completely non-intuitive."

Porsche had the perfect opportunity to really get the ventilation right with the 964. But, they left those slider controls intact (from the 944 right?). They seem almost worse than the previous generation's slider controls. At least those were marked with either hot or cold air and wasn't too hard to figure out once you read the manual 48 times...

After a year, I still haven't memorized which lever goes where to get which airflow in the right place...

Drew_K

If you think the 964 slider controls are confusing, check out the system on the pre-964 911's. The slider controls have slider controls, and there are also control levers between the seats.

Viken

This is the "MAX" button which is designed to give you as much cold air as possible when you first get in the car on a hot day. This button activates the A/C compressor, puts the system to the recirculating mode and the fan at the highest speed. No overrides are permitted.

The recirculating button is supposed to stop outside air from coming into the car and allow inside air to recirculate. This, usually provides cooler air but you must not use it for prolonged periods of time.

Bob D.

As usual, Randall is right on the money. The original climate control unit, at least on my late '92, had a single "snowflake" button on its left side. This unit died an early death in many cars (mine included), and is NLA.

The updated unit (which I believe is directly from the 993) has the 2-button setup with the 1-touch, max cool function described above.

Regardless of which control unit is directing the air, I must admit it is a thrill to have a 911 with a/c that works and works well! ;-)

Riccardo

Well,

I have a different theory altogether. I remember one of the cars I saw had the 4 buttons (total) on the a/c (as opposed to 3 which is what most of us have, or even 2 for those without a/c). Funnily enough it was also on an Amazon Green C4, but this one a 92 model.

I was under the impression that it was an option available to boost the a/c, a bit as Randall and Viken point out. This may also explain why your manual does not have it. I have a 93 car and it has only 3 buttons, and there is nothing about a fourth button in the manual. The manual is the 12/92 version.

Also, I confirm the same behaviour as you guys for the recirculate button. There is no change in air flow.

Randall, I am sure that the skunky smell came from other sources. Air always comes in from a number of different places, so even the recirculate button will not be able to completely cut that strong smell away.

Robert, what options do you have under you bonnet, maybe the dual a/c button (snowflake) has a corresponding number?

Adrian

Dear Robert,
The two snow flakes button is the replacement 993 control unit. In the 964 the second button, I think the top one overrides the speed control of the LH BLower fan. Max blow. Basically works like the defrost function does on the RH Blower fan.
The recirc button shuts the fresh air flapper valve and cuts off the supply of fresh air to the interior and to the mixing chambers and directs interior air into the mixing chambers instead. This function is used to remove external odours like diesel fumes when following those horrible mobile homes.
Ciao,
Adrian
911C4

Randall G.

Hi Riccardo,

I think is mainly (hopefully) true, but ... on page 57 of my '91 owners manual, after describing maximum cooling (which includes running the A/C and pressing the recirculation button), it says:

"Under normal conditions the system will always mix in some fresh air to maintain air quality."

On the other hand, the manual also says on page 57, in describing operation of the Air recirculation switch:

"press the air reciculation switch to shut off the flow of fresh air."

So, it appears to me that the recirc. button doesn't completely cut-off outside air--at least when running the A/C. And, considering how overpowering skunk road-kill can be, it's possible only a minuscule amount of outside air would have given the cabin just a hint of essence of skunk .

What I don't know is how much outside air is mixed in to "maintain air quality" .

Thanks for checking operation (air flow) of your recirculation mode. It does make me feel better, and it appears my recirculation mode is operating normally.