Front windshield defogger

Ok, a little backstory: I’ve had the truck now for 18 months and love almost everything about it. I live in the southeast and I’ve probably had a total of 4-5 days total, since purchase where this has actually been a problem.

it was pretty dang humid this morning and the windshield was fully fogged. A quick windshield swipe fixes the problem for about 20 seconds but it goes right back to dangerous driving conditions after. I engaged the defogger which turns the fan speed up and pulls in outside air automatically. I have a 10 minute drive to work. The attached picture is what the windshield looked like after I parked at work this morning. Almost no improvement whatsoever.

Do I have a defective defogger somehow? Is there a setting I’m missing. I’m really tired of bringing the truck to the dealer and having them tell me they can’t fix something because they can’t recreate the problem. Thoughts are much appreciated.

 

i'm strictly only a sexpert, so i'll do the best i can in this instance....

it pulls from outside trying to get the temps to match because thats what contributes to the fogging.
when doing this, i believe (not 100% sure) that it passes through your cabin air filter. verify it's not dirty, have a film on it, blocked, etc. to make sure it's getting the proper air flow and quality to your windshield.

is there anything you put on your dash that could be off-gassing onto your windshield? not sure, but that may be something too (kinda pulling at straws on this one)

verify your glass is clean in general. it looks like it may have a slight film on it from the pics, but that could very well just be deceiving from pics.

if need be, there are "anti-fog" window cleaners/treatments you can do, but that typically can be a rabbit hole and/or temporary fix.


hope this helps....or maybe someone with more knowledge can chime in and debunk me and help you more.

 

Add heat! Windshield is colder than the surrounding air causing condensation.
Add heat on defrost.
Almost 70 this morning and I had to add some heat on defrost to get the outside windshield cleared, so it's just normal.
If you just have the defroster blowing cool air on the windshield your adding to the problem.
*defrost will turn on the ac by default*

 

It does, but it doesn't have to.
I just posted this in a different thread (related to how cold AC is) and you can see in the pic below that the 2nd option can be changed in Techstream to NOT turn AC on automatically, when 'defrost' button in used.
Since the vast majority of fogging up cases are resolved with cold air, this setting is ON by default.
...no idea if OP or anyone wants this behavior changed permanently-I guess it really depends on use case.

Side note:
I changed my "set temp shift" to -2 degrees, but I also turned OFF the "blow up function."
No more fans at full speed as soon as I hit that defrost button!

 

Is techstream open source? If so, are there 'how to' videos on youtube that I'm missing? If its a paid program, I assume something like carista would work similarly...

 

Techstream is a paid/subscription Toyota tech software, and it ain't cheap.
There are alternatives to obtaining and using it, but I won't provide instructions here.
Gotta do your own homework on this one.
What you do need is a ODBII to USB adapter (some work, some don't), laptop, and said Techstream software.

...and while Carista can do some of the same changes as Techstream, it can't do them all.

 

Thank you. Points me in the right direction.

 

While easily obtainable for a fairly low price, even from a certain huge rain forest online retailer, do familiarize yourself with installation procedure and perceived risks, at least according to some people.

I have/had no reservations about installing it, drivers, etc and it runs just fine on my normal Win11 laptop. Some people run clean Windows on spare/new drives, disable connectivity, etc.
I'm not as paranoid, but I probably have a lot more experience in IT/networking than most here.
Have fun.

 

Exactly. It turns on the AC by default because that pulls moisture out of the air. At the same time, as mentioned below, you need to add heat. Then you get warm dry air for the best defogging possible. Once the windshield temp gets above the dew point your problem is solved.

 

do you recirculate air too while warming windshield?

 

also to piggy back on this great break down. this also helps during the winter when no one uses the ac. defrost also helps cycle the ac system even when its cold out so it doesnt sit idle for 4-6 months at a time.

 

Never use recirculate when your window is fogged up! Fresh air with a little heat should cure the problem.

 

So adding fresh air with high outside humidity
will work?