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Hi, I have a ‘95 993 C2 and it has an issue where damp air gets into the cabin when the car is started having been sat in the rain. It takes a minute or two to come through, but everything in the car mists up and it all comes through the vents.
I have repaired the mixer servos in the footwells and the fresh air mixer servo in the front with kits from Germany, and they work when tested with a 9v battery, but the CCU control unit needs attention as the fresh air servo doesn’t work when connected to the CCU.
The fresh air mixer is stuck in the position pictured above. Is this stuck open or closed? If closed, is there anything else that would be causing damp air to get into the air system? A drain or something?
Any pointers at all would be greatly appreciated. Thanks.
The servo is in the pictured position when the key is out of the ignition.
My experience is that it turns 90 degrees and lines up with the slot in its mount so it can be removed when the ignition key is turned to the on position.
Since having moisture entering the hood intake is the most likely place for moisture to enter and you seem to have confirmed that the servo is rebuilt, I would consider just servicing the CCU and inspecting the flap in the process once returned to you.
Also, check around the cabin air intake in the engine compartment and the heater flappers/ ducts on the underside of the engine as I seem to recall that in heavy rain a lot of moisture may get sucked into the system in the back.
Finally if while running the AC you do not see a puddle of water form on the ground directly under the center of the dash then the drain in the evaporator compartment is clogged and moisture may be backing up. It seems like a really easy DIY fix to snake the hose out
If everything checks out and the problem seems to only occur in heavy rain no action may be needed, it simply may be a feature of our cars.
A steamy cabin is the primary reason I can't run my 993 through the typical automatic car wash as following this for the next fifteen minutes I can't see anything out of the windshield.
Thanks Andy, as I say I repaired the servo motors with new internals as kits. The fresh air only moves to what I believe is the closed position and stays there. The CCU may be faulty, but I’m pretty sure that the flap is now permanently stuck closed. So where would the moisture be entering the vents?
I take it that the drain can only be cleaned out from under the vehicle? Or is there a way to access it from the top?
The fogging has nothing to do with your HVAC servo motors, but is a completely normal phenomena in air cooled cars.
The engine lid opening allows for a lot of water to go into the engine bay when parked outdoors in rain. When the wet engine heats up after cold rainy night, huge amounts of hot humid air will be produced in the engine bay.
If you have the cabin temp set to anything above minimum, this extremely humid air will be sucked into the cabin from the engine bay through the heat exchangers. When this air hits the cold windows they immediately fog up due to the condensation on the cold surface.
The trick is to set the Climate Control temperature **** to minimum before turning on the ignition and keep it there for about 2-5 minutes after you have started driving in order to vent out all the humid air from the engine bay before turning up the heat. All air will then be drawn from the front fresh air intake, and have the same temperature as the windshield. No fogging.
If the fresh air flap is permanently closed due to a fault, the HVAC fans will have nowhere to draw air from if you set the temp **** to minumum. This results in wheezing noises when the fans try to draw air through closed HVAC flaps, as well as a drastically reduced air flow.
Cheers,
Tore
If you go to this link, scroll down one page, select your model/year, and drill down to main group 8, sub group 13, illustration 813-10, you can see the parts of the HVAC water drain system. If you remove one of the cabin air filters, you can see down inside the "suitcase" that surrounds the AC evaporator, and any standing water that might be backed up in there. I haven't done it, but I think you could gently flush this out with a garden hose, see how the flow is coming out under the car, and maybe clear any clogs from underneath with a piece of coathanger. Just be careful of the check valve, shown as item #13.
It is probably too convoluted to try this from above.
10-20-2019, 10:14 AM
HVAC Damp Question
