Oh my my my, how little you understand about vehicle environmental controls.

I just had the opportunity of riding with a neighbor today, his heat and air conditioning work perfectly, but nothing he did would defog his windshield. The ventilation direction controls are apparently faulty on his SUV.

Why? Because the controls that direct the ventilation flaps are controlled with vacuum lines and multi-direction vacuum control dials. Any one vacuum line or vacuum control dial out, well guess what, air goes to your feet, not the windshield, even if that’s where he set the dial.

Either hot or cold dry air can help defrost/defog the windshield, but the air has to be routed to the windshield first, not a faulty control that routes it down to your feet…

There’s more than the switches at play, there’s heat, cold, thermistor controlled A/C, and vacuum operated ventilation flaps that actually direct the airflow.

One faulty vacuum line means the difference whether the airflow goes towards the windshield or towards your feet.

Please learn at least some of the complexities of vehicles before assuming a damn thing.

There are no rear window defogger wires, I’m talking about the front windshield defogger vents.

DEANZ

FTFY, also upvoted 🫘

I do think we’re talking from different generations here, and under the assumption everything even works. Yes, it is wonderful when everything works correctly, but even in that case, older vehicles had separate controls for the vents, the heat, and the air conditioning.

We got a '96 Sonoma, missing the entire right side of the dashboard, so no glove box, no blower motor, and half the missing ventilation system is duct taped over. Thanks to the previous but now deceased owner. :(

But at least the windows roll down in the heat of the day, and at least some of the ventilation system gives us heat in the cold when the vents are set for open air.

Yes we’re driving what most would call a shitbox, but it’s reliable at least.

I’d try to fix the dashboard shit, but that would probably cost more than the truck itself. So, back to simple brain mode…

• FROST: Warm up the engine, even if the AC worked, like why? Just warm it up a bit and drive…
• FOG: Wish the AC worked, but at least the windows roll down…

None of that stuff works when you inherited a truck that’s missing the blower motor, entire passenger side dashboard, and all relevant passenger side ventilation ducts.

Yes it’s a shitbox, but otherwise runs great. Just no luxuries, no air conditioning, due to no blower motor or half the ventilation system. Also the heat only works while driving, also because no blower motor.

At least it’s otherwise reliable, plus also has manual roll down/up windows.

Long story short, AC is for drying air, not just cooling it.

No shit, that’s my entire point.

Not everybody has fully working AI based environmental controls, some of us from Pepperidge Farms remembers when the controls were separate and not exactly automated the way lazy fucks expect these days…

Thank you for the advice you leaking Tide Pod, there’s literally a fucking button…

“To effectively use the defrost and defog controls in a 1996 GMC Sonoma, press the Defog/Defrost button, turn off the Recirculation button, set the fan to the highest setting, and adjust the temperature to high. This will help clear the windshield quickly.”

Anyways, you drive and troubleshoot your vehicle, and we’ll drive and troubleshhot ours. They’re not all designed the same you muppet.

Well I take it we’re not in your state or country. Mississippi here, we no longer have vehicle inspections. And this is respected even in other states that do require vehicle inspections. They’re like yeah fuckit, half the windshield is cracked, but it’s from Mississippi, so nothing Louisiana can do.

Down here, we’re half-professional rednecks that try our best to keep our own vehicles running. As long as it starts, runs, stops, shifts gears, steers, and has all the critical lights working, it’s fine.

Hood, trunk, windshield, front grill, rear bumper, doors, heat, air conditioning, etc luxuries are all optional here. As long as it runs, stops, and steers is basically what all Mississippi cares about, plus lights at night. And other states have to observe our very lax vehicle requirements too.

I’m still working on some of the finer things, like it needs a horn, but generally speaking the truck runs pretty damn good to be 30 years old.

deFROST != deFOG

• deFROSTer is meant to melt frost, ice and snow off the windshield, uses heater.
• deFOGger is meant to dry fog off your windshield on hot humid days, uses air conditioner.

I’m starting to gather that most people don’t have any clue how to properly use their environmental controls.

And this is the proper way.

Does absolutely nobody understand the difference between FOG vs FROST?

• The deFROSTer is meant to gently melt snow and ice FROST off your windshield using the heater. Kinda fucking counterintuitive to blow freezing air at a frozen windshield, the FROST will never thaw that way.

• The deFOGger is meant to dry the humidity off your windshield on a hot humid day, that uses the air conditioner on hot humid days.

Two different systems, for two different climates. deFOGger vs deFROSTer are two completely different modes of the climate controls.

Do people understand the difference between FROST vs FOG?

• Frost happens in the cold, best mitigated with gentle heat.
• Fog happens in the humid heat, best mitigated with air condition cool dry air.

FROST != FOG

Knowledge is never irrelevant if you’re still driving around a 30+ year vehicle. Knowledge is relevant across all years, here’s reference from 1960-2025 year range vehicles. I’m not fucking retarded…

https://lemon-manuals.la/

What I do know, first hand experience, is if the air conditioner goes out before the heater core heats up, well you got about 15 seconds to roll the windows down for airflow to keep the windshield from fogging up.

The entire right side of the dashboard is missing, all the way down to the firewall, no thanks to the previous but now deceased meth tweaker owner.

There’s no fixing everything on this truck, short of dumping enough money into buying 4 more scrap trucks for spare parts…

I said 90’s through 2000’s, I said nothing about 2010’s or beyond.

I do not have much of any experience in working on anything past 2005.

Anything past 2014 is what I call new generation enshittified, as that’s around the year they basically started tracking everyone, refusing to offer printed service manuals (Hayne’s/Chilton), stop offering parts and requiring ‘owners’ to take the vehicle back to the dealership for repair.

I’m all about the right to repair. Your 2015 is a new generation enshittified thing, sorry.

Our heater does work, just no blower motor, so if we need heat, just open the vents and drive for airflow.

Our air conditioner unfortunately does not work, but we have manual windows that roll down by hand for airflow.

And today I just happened to install a fan on the dashboard.

Yes it’s a piece of shit truck, but ignoring the ‘luxury’ features that cost more than the truck itself to fix, it’s pretty darn reliable.

See my previous posts regarding Kermit the 96 Sonoma for reference. More reliable than new model Ford trucks that brick themselves because rainwater got into the taillight assembly…

Yeah… no… that’s only the newer generation of vehicles, the enshittified ones that assume everything for you.

Back in the 90’s and 2000’s, the engineers had common sense and if the temperature dial was set anywhere above 50%, the air conditioner would never turn on, as it’s a waste of energy at that point.

I think you got the right idea, just backwards…

Assuming your heater, air conditioner, and blower motor all work correctly, you should use your heater defroster in cold weather, and your air conditioner defogger in warm weather.

Note the difference in environmental control terms…

• DEFROSTER > Used for cold climate, heater, to melt the frost off your windshield.
• DEFOGGER > Used for warm humid climate, air conditioner, to dehumidify the air.

Failing either heater or air conditioner, welp, just do what we do and roll the windows down.

People in comments assume the heat or air conditioning even work.

Air conditioning also rapidly reduces humidity, so that tends to be the ideal option.

But if neither heat nor air conditioner work, well tough it out and roll the windows down…

Tomorrow happens to be my birthday.

Your comment reminds me to get an air horn…

📯