Nittany

I have had my Porsche 2006 911S for 2 years now. I bought it used with only 6k miles on it. Since I usually only drive it when the weather is fairly nice, I never had to use the front defroster.

Well a few months ago, I drove it in rainy weather, but it was quite hot that day. I had the AC on LO at mid-fan level. My windows began fogging and so I decide to use my front defroster for the first time. Steamy hot air came out even though the AC was set on LO.

Thinking something was wrong, I took the car to the dealer and after leaving it there for a half a day, the mechanic told me it was a normal function of the car. He said the purpose of the front defrost is not to be left on but only for a short period.

Is that normal or was the mechanic pulling my leg?

ADias

When it is very humid that can happen. I would expect though that if you had the AC on in Auto, after a short while the fogged windows should have cleared.

BTW... it is a good thing to use the AC often, even in the Winter. Unused ACs go bad.

Nittany

But is it suppose to blow out extremely hot air? I could see initially the air maybe hot, but after a few minutes the air should cool down with the AC on. I could barely stand it because it was over 90 degrees out side and it felt like 100 degree inside my car with the AC on.

Just doesn't seem right. Does all the 997s do that?

ADias

No it does not seem right.

Mike in CA

The explanation about not leaving the front defroster on for extended periods being the cause of your problem is ridiculous. Pressing the front defrost button should duct air to the windshield only, that has been dehumidified by the AC. You certainly shouldn't be getting hot steamy air.

draxa

The "Defroster" is designed to do exactly that - defrost. Specifically in cold, frosty, icy countries where a hot blast is needed.

For regular demisting, just use the fan on low (A/C off) with the arrow pointed up and it works like a treat.

Edgy01

What the mechanic told you was precisely what I experience and my way of also using the 'defrost' function. Quite often when I go to get into the car after an evening out I will notice that there is heavy condensation on the lower portion of the windshield (inside) which must be from a high humidity situation (below the dew point). As soon as I start up the car I push that button. It immediately diverts all heat to the windshield area and in no time that stuff is dried off. I can quickly then drive away. (Without it I couldn't see the road ahead). Once it has dried off the windshield I turn it off and then allow the normal a/c to do it's thing about keeping the windshield free of condensation.

ADias

I did not pay attention that you are using defrost. Yeah that can blow hot air. For condensation just run the AC in Auto.

BobbyB

Typically the defrost is like turning on the heater, with air directed at the front windshield. The AC basically is not working while hot air is directed at the windshield...no wonder it felt like 100 deg inside-to be expected. Once he window is clear, turn on the defrost and the AC will go back to work.

Mike in CA

I don't think that's correct. Try this. Press the "AC Off" button and it's light comes on. Now engage the windshield defroster. Air flows only to the windshield and the "AC Off" light goes out. Disengage the defroster and the "AC Off" light comes back on.

What this tells me is that the AC comes on when the front defroster/defogger is turned on. (The manual refers to the "defroster" as performing both defrost and defog functions). This makes sense because the AC dehumidifies the air and causes the windshield to defog more quickly. My Audi and my wife's Highlander work exactly the same way.

That's why it doesn't follow that the OP should be getting hot "steamy" air when he turns on the defroster. It may be hot, depending on the automatic temperature setting, but because of the AC, it shouldn't be "steamy".

Holli82

can't help you

live in the desert and have NEVER used the defroster (front or rear). Never used headlight washers either.

any A/C questions????

BobbyB

Mike, sounds like we are both on the same page. I never take my system off of "auto". When I turn my defroster on, it does what it's supposed to do, the air to the normal vents is reduced greatly with hot air hitting the windshield. After a few minutes, I turn the defrost off, and everything goes back to normal. Most of these systems are designed to work as I've described above. Nothing wrong with turning the AC off and doing it in two steps.

Mike in CA

Bobby, not to make a big deal of it, but the one thing I disagreed with was when you said that the "AC basically is not working while hot air is directed to the windshield", in other words when the defroster is on. I'm saying that it IS and should be working, and in fact even if the AC is off when the defroster is first engaged, it will automatically turn on. That's what my little "try this" experiment was pointing out. This is relevant to the OP because with the AC on, he shouldn't be getting "steamy" air. FWIW.

Macster

Others have addressed your question but I wanted to use this opportunity to mention that even if one lives in an area where the weather is mild or only drives his car in mild weather the A/C system should be used once in a while.

Periodic use helps keep the system seals from drying out and leaking refrigerant (and compressor oil). In fact, what I like to do is select the various vent controls to change where the cabin air is vented to exercise all the vent flap control motors. I run the heat up to max and then down to low and do the same for the fan speed control. This helps to keep the various flap pivots, control motors, etc., loose and helps prevent sticking from inactivity.

Be sure to run the A/C for awhile then turn the A/C compressor off while letting the cabin ventilation fan continue to run to dry out the A/C system from any moisture that may have condensed on the colder components of the system. This is escpecially a concern in area so rather high humidity.

Failure to do the above can result in the build up of mold/mildew in the A/C system which emits a smell that can be rather unpleasant and hard to eliminate.

Sincerely,

Macster.

BobbyB

OK...