best way to defrost?

Hey there, starting to get frosty in my part of the world and just wondering the best way to defrost the windshield?

First off, I'm not that dumb, I know there is a couple of options like the windshield/floor or windshield only selection, but in my 2012 the floor only selection also puts heat on the windshield without having the a/c on. Works pretty well too. The operators manual even shows this works.

experiences? or do everyone just throw the switch to windshield only when the temperature drops?

 

I did the mod to disable the automatic A/C with defrost. Now I get full heat to the windshield for frost, but can still manually turn on the A/C for foggy/dew windshield mornings.

Barring that, I would still go with full windshield for best results with frost. I just hate the fact that they forced the A/C with defrost on us. I know it works good with dew, but some of us have to deal with sub freezing temps, and definitely do not want A/C in January.

 

Yeah I know, but it seems almost all cars are like this now. I wish I had the choice to use the ac or not.

 

I just leave mine on floor/windshield all the time. Works all year 'round, and the only adjusting I have to do is cold/hot. I barely even turn on the A/C in the summer.

 

I'm not really understanding this. A/C on or off, hot air is hot air so I don't understand why you'd care if the a/c button is on? Also, I hope you all aren't relying on only the defrost to clear your windshield? Between an ice scraper, ice melt washer fluid, and the defrost I never have issues with the window.

 

When the A/C kicks on the hot air is reduced to lukewarm air. The A/C obviously cools the air down. And yes, I rely mostly on defrost to clear the windshield. On very icy days I have to scrape as well if I don't have time to let the defrost do its job. Not sure why that would surprise you because that is what defrost is for.

 

If I have the AC on and the setting on vents, then switch to windshield, the AC turns off!!

 

Yeah, I'm not going to get into an extended argument with you but that's not how the a/c works. It doesn't cool down the hot air, it is just making it drier. Try it, put a thermometer in your vent if you don't believe me. And yeah, I know what defrost is for, I'm just saying why rely only on it when you can do the job a lot quicker with a scraper and washer fluid along with defrost.

Last point I forgot to make, if you heat your windshield too much, too quick you risk cracking it. I've had this happen to me twice in the past, the first time I never noticed it but the second time I actually saw the crack happening. Maybe the glass was already weak or maybe a small pebble hit the glass that I never noticed but either way both times it was in 20 degree weather and I heated the windshield really quickly.

 

I don't need a thermometer, I could feel the temp dropping with my bare hand when the defrost was turned on. If you don't think so then go put your hand on the A/C feed tube under the hood with the defrost on, it gets extremely cold, which means it is cooling the air. Many people on this site have done the mod to disable it, so you are saying we are all wrong and you are right? Sorry, but you are wrong on this one.

 

I just throw it on full windshield for 10 min before I leave and that's it. Didn't realize people put that much thought into it haha. I'm lazy and only scrape if there is actual thick ice from freezing rain or sleet.

 

+1. I'm guessing the reason the A/C kicks on is because the drier air, in very cold temperature, will actually reduce the condensation on the windshield faster than hot air with a lot of moisture on it, which in theory could condensate (and even re-freeze if you turn off the defroster later). IMO, leave the AC on while you defrost, then once the windshield is clear, turn it to windshield/feet or just feet with residual to the windshield, and turn the AC off.

 

Good 'ol butt (hand) dyno. I bet you can feel the HP increase from your K&N cold air intake too

 

x2... I guess I don't see the need for an extended discussion on the topic.
Step 1 - Start the vehicle
Step 2 - Turn temp setting to hot (red side)
Step 3 - Turn HVAC setting to defrost (setting that looks like a windshield with bacon)
Step 4 - If you read this and actually learned something, turn off the vehicle and go back inside, you should not be operating a motor vehicle...

 

It might get cold because it's condensed moisture being exposed to cold air? The fact that that tube gets cold tells you nothing about the air being pumped into the car. The whole point of AC is to reduce moisture (as already stated). And the drier air absorbs the moisture from the windshield better than without AC...hence making it defrost quicker.

 

+2 No noticeable difference in heat for me whether a/c is on or off, just drier air

 

You are absolutely correct, when we are discussing condensation, as I stated in my original post. Not so much with solid frost/ice on the windshield which needs to be melted, not 'dried up'. Since doing the disable A/C with defrost mod my windshield gets free of ice much sooner. I'm not the first person to notice this, but whatever works for you all go with it.

 

Lot of false information here.

First the A/C evaporator only gets down to between 35-40F.

If the outside temperature is below 35-40F the A/C is actually preheating incoming air because it is colder.

Because the air outside is already colder the A/C does not dry the air (remove condensate). It can only dry air if it is warmer than 35-40F outside.

I personally haven't bothered with the A/C off mod but I get good results using the middle position that shows floor but distributes to the windshield also.

If outside temp is -15F with A/C on you get 40F air to your windshield immediately.

And yes the A/C evaporator is before the heater core so no it doesn't first heat the air and then cool it with A/C on.

 

Some people just can't leave the truck to do what it is designed to do. He does not understand why the a/c comes on so he will end up reducing the life of his a/c system.

It does that so that your a/c system gets lubricated in the winter because everybody knows in a cold place people will not turn on the a/c to keep the compressor lubed. And it only cycles and does not stay on the whole time you have the defroster on.

Me I just get new cheap wipers every first snowfall (Nov/Dec) and I use the bright yellow fluid that is good down to -35. I have had it work great at -20 before. Just give it a squirt right at start up and turn the wipers right back off. After the truck runs for 1-2 minutes everything wipes off good. I also have a can of the instant defrost but rarely have ever used it.

Another good thing for winter. Ever had your locks freeze up? I spray LPS #3 in all my locks and have never had one freeze up since. Works great.

 

Good point, but actually I understand perfectly about cycling the A/C to keep it running properly in the colder months. I do it manually several times per month in the winter.

 

Your AC will never get it to Sub zero temps. The AC system typically works at around 35 degrees. If your outside temp is actually -15, then the A/C would be HELPING warm it up.

As mentioned, the difference is between hot DRY air, and hot HUMID air. Dry air defogs better. I agree on the OUTSIDE of the windshield. Use a scraper.

Bingo

It is not designed that way at all. The sole purpose of the defroster "compressor on" operation is for defogging/defrosting of the windshield. Pag-oil is good to almost -100 degrees, and your compressor is in a sealed environment. It is not going to lock up just because you never use it in the winter.

You are right about it cycling on defrost, but it cycles all the time. Even in the summer. The compressor never runs at 100% duty cycle all the time. What happens is when the low pressure sensor drops to a predetermined pressure, the system will shut off the compressor until the pressure raises back up into the safe range. This can sometimes only take 5-10 seconds. This is done to prevent the evaporator SURFACE temperature from dropping below freezing, thus freezing the condensation that builds up, and blocking the path of the air.