964 - Heavy Fogging in Rain
01-26-2018, 05:00 PM
#1
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Thread Starter
964 - Heavy Fogging in Rain
Hoping for a little bit of help...I have a '91 964 C2 Coupe that I use as my Daily Driver. On rainy days (even lighter sprinkling) the windows fog completely over. I have to run the front and rear defroster 100% of the time to maintain even limited visibility.
I'm sure this means that I'm getting moisture into the cabin and HVAC system, but I'm not sure if it's just air pressure and temp related, or if there is actual water seepage occurring (I don't see any visible signs of actual water entry such as soaked floorboards, etc).
Question 1: Is this amount of fogging normal in cars of our vintage?
Question 2: Any culprits to check or suggestions?
I'm sure this means that I'm getting moisture into the cabin and HVAC system, but I'm not sure if it's just air pressure and temp related, or if there is actual water seepage occurring (I don't see any visible signs of actual water entry such as soaked floorboards, etc).
Question 1: Is this amount of fogging normal in cars of our vintage?
Question 2: Any culprits to check or suggestions?
01-26-2018, 05:22 PM
#2
Rennlist Member
The windows fogging over inside is due to water vapour condensing on them. For this to occur there has to be water vapour in the car. This could be from your breath, water on your clothing or more likely water trapped in the interior. I’d check the soundproofing very carefully as it can hold a lot of water without being obviously wet. Another possible source is poorly sealed membranes in the doors or a ripped speaker cone.
01-26-2018, 05:38 PM
#3
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Rennlist Member
When it rains are you running the air conditioning?
01-26-2018, 05:43 PM
#4
Rennlist Member
Could it be that one or both of the hoses from your heat exchangers to the chassis are not connected properly or have holes in them?
Last edited by Vegas993; 01-26-2018 at 08:30 PM.
01-27-2018, 03:49 AM
#5
Rennlist Member
You might have a problem with one or more of the HVAC servo motors. These are known to fail, and can severly impact the air flow to the cabin. You also might have a problem with the rear fan. See this page for a DIY test procedure.
As a side note, it is normal to see a lot of fog in the air cooled 911's at startup in rainy and cold weather. If the engine is wet, and you have set to Defrost or heating on the Climate Control Unit, very humid air will be drawn from the engine compartment. This will be blown onto a cold windscreen, causing it to completely fog up. However, when the engine/heat exchangers are warm, the problem will (shall) go away, normally in 1-2 minutes. A workaround is to set the CCU to minimum temperature before startup, and turn it to a normal/hotter setting when the engine is warm, and the water vapour in the engine compartment is gone.
Cheers,
Tore
As a side note, it is normal to see a lot of fog in the air cooled 911's at startup in rainy and cold weather. If the engine is wet, and you have set to Defrost or heating on the Climate Control Unit, very humid air will be drawn from the engine compartment. This will be blown onto a cold windscreen, causing it to completely fog up. However, when the engine/heat exchangers are warm, the problem will (shall) go away, normally in 1-2 minutes. A workaround is to set the CCU to minimum temperature before startup, and turn it to a normal/hotter setting when the engine is warm, and the water vapour in the engine compartment is gone.
Cheers,
Tore
01-27-2018, 11:05 AM
#6
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Thread Starter
Thanks for the suggestions...definitely gives me some options to explore. It seems to have gotten worse over the last year, regardless of season (summer, winter, etc). There’s no doubt moisture is getting in, just not sure if it is due to a failing system (blowers, hoses, etc) or a water leak into the cabin.
Any common areas to check for leakpoints? In the meantime, I’ll explore the fan test from Tore.
Any common areas to check for leakpoints? In the meantime, I’ll explore the fan test from Tore.
01-27-2018, 11:21 AM
#7
Rennlist Member
To elaborate, when I got my car it had a poorly connected heater hose and fumes were coming into the cabin. If you're driving in rain, it's possible the heat of the engine mixed with wet roads could be creating a steam effect and entering that way as well. Easy fix if so!
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01-27-2018, 12:50 PM
#8
Hi all
I would also be interested in hearing the leaky places on 964. I recently moved to a much wetter climate. Would like to drive the 64 year round but I find it gets a bit wet on the carpet in the rain so I have been keeping her in the garage more than I would like. Obviously I dont see any actual leaking on driving.
Thanks
Rob
I would also be interested in hearing the leaky places on 964. I recently moved to a much wetter climate. Would like to drive the 64 year round but I find it gets a bit wet on the carpet in the rain so I have been keeping her in the garage more than I would like. Obviously I dont see any actual leaking on driving.
Thanks
Rob
01-29-2018, 03:30 PM
#9
Rennlist Member
+1 on all suggestions above.. also check that your evaporator drain plug is clear. Does your A/C function? Running A/C will tend to dry out the air, but the water that condenses needs a place to drain to. Under the car there is a metal cover for the fuel pump. In that same area there is a rubber drain mechanism for the evaporator pan. Compressed air or a gentle poke with a wire might help.
04-18-2018, 11:16 PM
#10
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Thread Starter
Just an update for those that are interested...Checked the ingress points and everything looked clear. I took it to a local specialist and he ran a thermal image which indicated a major gap at the drivers side door. Apparently a P.O. had pried the door open at some point (left an interior mark too). The thinking is there is water running in from this gap, soaking the carpets and creating the fogging.
I’m picking it up on Friday with the door properly fit...will keep updating on if this is the fix or not.
I’m picking it up on Friday with the door properly fit...will keep updating on if this is the fix or not.
04-19-2018, 02:54 AM
#11
Just an update for those that are interested...Checked the ingress points and everything looked clear. I took it to a local specialist and he ran a thermal image which indicated a major gap at the drivers side door. Apparently a P.O. had pried the door open at some point (left an interior mark too). The thinking is there is water running in from this gap, soaking the carpets and creating the fogging.
I’m picking it up on Friday with the door properly fit...will keep updating on if this is the fix or not.
I’m picking it up on Friday with the door properly fit...will keep updating on if this is the fix or not.
Lift the floor mats, and actually lift out the thick foam that is underneath. There is a high chance it will be full of water. Remove these, dry or toss them (Cup floor boards are a godsend). Lift out the rear seat bases as well.
By then the car will be drier inside, reducing the fogging.
Then tackle the possible water ingress points.
