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Typical causes for AC condensation in vent on my 87

Last night, took the 87 Targa with top off out for a spin at 8pm and noticed water dripping out of the ribbon vent under the dash. AC was turned on mid-level, blowing about 55+ degrees F and humidity was about 81%. I turned AC off and it dried up

First time I have noticed this. Note that the AC holds charge but doesn't really blow lower than 55 degrees. Using existing dryer and other hoses are original I believe. I eventually plan to upgrade the system, but just waiting a few months.

I know AC systems create condensation - but not familiar with these cars yet on this and wondered what typical root cause might be to result in this.

TIA for any thoughts.
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Old 07-15-2019, 06:20 AM
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there is an air leak in the vent in the dash probably
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Old 07-15-2019, 06:25 AM
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Originally Posted by T77911S View Post
there is an air leak in the vent in the dash probably
Thanks. So the vent that is actually leaking (bowtie vent under dash) or one of the vents that blow on driver/passenger? Just learning so don't know exactly where that could be.
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Old 07-15-2019, 08:29 AM
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Sounds like you need to clean out your evaporated drain hose. Excess water is getting blown out to the vents.
Old 07-15-2019, 09:56 AM
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that's possible too
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Old 07-15-2019, 10:25 AM
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Quote:
Originally Posted by RSTarga View Post
Sounds like you need to clean out your evaporated drain hose. Excess water is getting blown out to the vents.
Thanks. Is this the hose you are referring to (#2 in the pic below)? Its longer right and goes out to the underside of the car?

Believe its this part: https://www.pelicanparts.com/More_Info/91157122300OEM.htm?pn=911-571-223-00-OEM&bt=Y&fs=0&SVSVSI=0815

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Old 07-15-2019, 10:28 AM
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No, that is the vent drain. Get your car on a lift and you will see a hose end coming out under the evaporator. This is at the front of the passenger foot area. Push a wire up or better, vacuum out with a wet vacuum cleaner. You will be surprised at the amount of water that will come out.
Old 07-15-2019, 12:22 PM
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No, that is the vent drain. Get your car on a lift and you will see a hose end coming out under the evaporator. This is at the front of the passenger foot area. Push a wire up or better, vacuum out with a wet vacuum cleaner. You will be surprised at the amount of water that will come out.
OK, thanks. Don't have access to a lift easily, just jacking it up. Where does it connect then on the car? Is it where I have circled below in Blue? Or is it the one of the ones on the diagram below it? TIA


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Old 07-15-2019, 12:37 PM
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Could also just be humidity in the air condensing on cold ac parts (in this case the vent). Might not be internal.
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Old 07-15-2019, 01:11 PM
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Could also just be humidity in the air condensing on cold ac parts (in this case the vent). Might not be internal.
Thought about that as well. Very humid in the evening that night so wondering if that was causing it. However, still will check the hoses - eliminate all possible causes...
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Old 07-15-2019, 01:27 PM
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You don't have to disconnect it from the evaporator box, just access from under the car and poke a wire through. Dirt, together with condensate tend to plug the drain.
A/C is very effective at removing water from the air. Your home unit also has a drain that must be kept clear.
It should be normal maintenance item.
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Old 07-15-2019, 02:07 PM
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Well, I can't see fully under the car, so for now, improvised and took pics and pushed a wire hanger (didn't like that in case I punctured the line) and don't think there is anything clogged in there. Obviously, I need to do it the right way - but for now - seems clear. Also looked at other hose there and believe I am looking up at the evaporator?

Have a bore scope camera on the way for something else, so will try it as well maybe until I can find a lift.



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Old 07-15-2019, 09:22 PM
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Not an a/c guy but I suspect your evaporator is dirty & clogged. You can take a peek to see the evaporator fins by taking out the wooden passenger footrest. There is a cavity that sucks in air from the cabin to the evaporator.

A few years ago I sprayed some a/c cleaner on the fins from that cavity.

Last edited by mo-mon; 07-16-2019 at 04:06 AM..
Old 07-16-2019, 03:55 AM
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isn't some amount of condensation normal during humid conditions? All of my ac'd cars have on occasion let some fog out the vents, which is basically water vapor.
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Old 07-16-2019, 07:42 AM
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Quote:
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isn't some amount of condensation normal during humid conditions? All of my ac'd cars have on occasion let some fog out the vents, which is basically water vapor.
It was extremely humid and at night - so thinking that was main cause but good for me to look at all this stuff anyway. Its never leaked before that I noticed, but that doesn't mean something didn't happen in between. I believe most if not all of the AC system except for one barrier hose I can tell for sure is original. So it will need work eventually, but trying to survive without doing it.
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Old 07-16-2019, 08:19 AM
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I have seen HVAC systems create condensation off of a leaking air duct, just made me suspect an air leak in the ducting inside the dash.
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Old 07-16-2019, 09:19 AM
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Well, he did say he was driving with top off. Warm air hitting cold air will cause condensation.
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Old 07-16-2019, 10:19 AM
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A/c

Quote:
Originally Posted by Jgordon View Post
Could also just be humidity in the air condensing on cold ac parts (in this case the vent). Might not be internal.
Yup,

I have been to Texas a few times,
and the humidity can be intense.

One of the demons in any A/C system is humidity.

some of the fixes are:

1. Proper charging.

2. Proper ompressor cycling.

3. Running the fan at high speed.

I refurbished our A/C, new hoses all around
flushed out both condensers & evaporator,
new pump, new hi-low, ect.....

One of the posters is correct about evaporation
contamination/blockage.

When I removed the existing evaporator
it was full of crud.

Replaced the evaporator with high flow unit.

The replacement I used was from Rennaire in
Texas, but they may be no longer in business.

Other than, that, the system is stock.

With the A/C temp dial set on the #4 point,
and the fan set at the next to highest speed,
I get 40f on a 90f day.

The cycling is 52f compressor on.
42f compressor off.

Keep in mind that running the center duct temp
lower that 40f means that your evaporator is close
to 32f (freezing) which invites freeze-up.

A/C work can get very $$$$$$$.

pm me as needed, I'll try to help.


Best,

Gerry
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Last edited by 86 911 Targa; 07-16-2019 at 11:12 AM..
Old 07-16-2019, 11:01 AM
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