Alex Sol

With the 40 degree (F) weather up here in Toronto and when driving in the rain, my windshield venting cannot keep up with de fogging the front windshield. I can only get about 6 inches of clear glass at the very bottom of the windshield. Very dangerous. Any one have the same problem and suggestions for a fix?

dfinnegan

Sounds like your heater servos are not working correctly.

Check this link: http://www.porsche964.co.uk/technical/servos.htm

hawk911

I leave mine set this way all year round. Top slide all the way right, bottom slide about 1/4 off the left side. What do you have yours set to?

dfinnegan

I believe that pushing the defrost button changes all of the settings to full dash vent, full fan, full heat overriding the manual settings.

Alex Sol

I have my slides all the way to right on both sides. will try the bottom slide 1/4 way over. I have the windshield / defrost button on. A/C is not working so perhaps this is the problem?

hawk911

I HATE the defrost fan; too loud for running all the time. RallyDog gave me the slider settings, and I've not had trouble since. No defrosting required.

dboyle

Yeah my defrost button results in lots of noise and little defrost

The defrost fan runs for probably 5-10 minutes with no issues, than it sounds like there is a 747 in my dashboard spinning up for takeoff. No real change in effectiveness with the sliders so I think the defrost button negates any of the settings.

-Dave
______________
'91 Strosek C2 (supercharged)
'00 Honda S2000
'04 Honda Element (hey need a practical car for New Hampshire)

hawk911

Defrost must have a mind of it's own

Alex Sol

While cleaning up my garage, i noticed my two vents with clamps that i removed in the spring. Went to the shop, got the 964 up on the hoist and re installed the the vents that run from the muffler to the heating system. whoops! completely forgot that I removed them. Lots of heat now coming into the cabin and defrost situation working okay at current freezing temperatures.
I do need to replace a servo motor on the passenger side that controls the heat coming from the passenger side muffler / heat exchanger.
Does anyone have experience changing these out? Any special tools required?

I don't think those sliders do much with the defrost button on. It seems most of the air is diverted up into the windshield area.

BGLeduc

Exactly.

The issue is that the dewpoint inside the car is higher than the surface temperature of the glass, causing condensation. Its the same principle that causes a nice cold beer to sweat when removed from the fridge on a summer day. The beer bottle is your windshield surface; the air in your home is the air in your car.

The AC is what actually removes the moisture from the air; w/o it, you will never clear the windscreen. It is possible that hitting the inside of the window with enough hot air will eventually warm it to a point that is above the dewpoint, but it is doubtful that the entire windshield will ever get warm enough.

Edit: I forgot to mention that unless it is raining out, the outside air is likely drier than the air in the cabin, therefore you DO NOT want to turn on Recirc. But again, the real issue is that of needing AC to dehumidify the air.

Brian