2017 Prius Windshield and Door panel Moisture (EDITED)

classic prius problem, are you using heat or a/c to try and dry it out?

 

a/c is drier. water in a '17 would be unheard of, i think. in the past, if it isn't under the carpets, it's in the spare tire area.

 

When you demist, make sure the A/C is on? Someone was complaining about moisture building up a year or so ago on PriusChat, but it seems they were turning the A/C off when demisting.

 

just for kicks, check your 12v health, aside from the moisture problem, to make sure it isn't causing any of the other symptoms.

 

Replace the pollen/cabin filter they tend to absorb more moisture when they get dirty.

 

good thought, i would try more fresh dry air, even if it is colder.

 

Definitely the A/C OFF will be your problem. The demisting action of the A/C is much better than just heat. Heat creates steam. Which then re-cycles around the car.

With A/C on, the moisture will condense on the evaporator, and when the drips build up on the evaporator, it drips and exits through the drip tube onto the road. Have a look at a home air-conditioner - this is just a small bedroom one, it's 60% humidity, and this is how much moisture dripped into the dog's plate in 75 seconds. It will fill it within the hour many days (no I don't leave her to drink from it, but just to soak it before cleaning - though I've caught them both drinking from it, as it's 3 less steps than to their water bowls!!).

 

AC definitely clears condensation fast but I think the main problem is not allowing fresh air in, it's just recycling whatever moisture is in the car back around again.
I find messing about with the AC (on and off) causes more misting than leaving it on or off entirely.
I know this defies logic, but I find leaving AC switched off I don't get as much condensation as leaving it on when the climate is in AUTO and switching it on and off as required.
I haven't tried leaving AC on and using the climate in manual mode, but I suspect that will work equally as well.

 

It depends on the moisture content of the outside air. If you can use the A/C on Recirc, it takes the inside air past the A/C evaporator time and time again, each time taking more moisture out. If you let outside moist air in, you never win.

But, if your outside air has low moisture content, then you might find advantage with FRESH rather than RECIRC.

It's mid-summer here (was 34C today), so I can't test it, but I thought that if you pressed the DEMIST button, it closed the RECIRC and put A/C on - whatever it defaults to, seems to work OK.

We lived on the Atherton Tablelands for 10 years - initially with cars with no A/C, they would actually get musty smelling inside. We had to wash mould from our entire house at least once a year - twice if we had energy - initially with brooms, bleach and hard work - later with a high-pressure washer:


Driving at night was always risky because we didn't know if there would be heavy fog when it came time to go home.

But when I got my first A/C car in '76, I tried just about every combination - but VOLVO had it worked out in their handbook. It said to close outside vents and use A/C in conjunction with the heater to achieve a comfortable temperature - I guess it got a bit colder in VOLVO country than Atherton.

Some Pics (from GOOGLE) of Atherton Tablelands, in Far North Queensland:

 

I'm pretty confident you are experiencing condensation from respiration etc. Using the HVAC, or air-conditioner will remove that moisture to the outside of the car.

Not sure that will be true for climate outside of tropical rain forests and humidity is a constant 100%, but in more temperate climates the fresh outside air will be dehumidified by the chiller before entering the cabin. YMMV.

 

try this: keep recirc and a/c both always on. irregardless whether you heat or cool. and windows always closed. this setup will continuously make your cabin drier and drier. if this doesn’t work it means either the a/c isn’t working or you have a moisture source that is introducing it faster than the a/c can take it out. oh and if you see windshield fogging, check by using the wiper whether it’s on the outside or inside. good luck!

 

Sometimes a little water gets inside my 2016 door sill after it rains, and there's condensation on both front and rear windshields if the temperature dropped a lot after it rained.

Maybe that's what's happening.

Posted via the PriusChat mobile app.

 

The Gen 4 doesn't have the little channels on the roof like my Gen 2 did. So a little rain rolls/falls off the roof and down the inside of the window sill onto the internal door sill on the driver's side front.

Drilling a hole would definitely not resolve this issue. Perhaps a very fine bead of clear silicone caulk at the upper edge of the window sill might. What do you think?

It doesn't appear that water is getting inside the door itself. All the condensation is on the windshields. The defroster and defogger take care of it.

Posted via the PriusChat mobile app.

 

I find that with the slightest breeze blowing while it's raining (yup, it did happen in England ) open any for in the Prius and rain gets inside. There's no roof gutter so it just falls onto the seats.

 

Thanks @RCO, roof gutter is the term I needed.

Posted via the PriusChat mobile app.