Defrost A/C Toggle Mod

The great defroster controversy! It’s like OEM vs aftermarket LBJs.

For the record, I’m in with this one. I’m cheap and don’t run my a/c much.

 

Yeah I hear you. I call "defrosting the windshield" removing the condensation on the inside of the glass.

I've been driving in the CO mountains for nearly 30 years now. In all sorts of winter storms. 20 years in this truck alone. I've never had an issue with the stock defrost set up.

So, like I said for the third time , cool mod and write up. I just don't see the use for me personally. And that goes for the gray wire mod too.

 

Fair enough. That's how I feel about AC lol

 

Defrost only puts cool air when the temp is set to cool. The rest of the time it wont put out cold air but still removes moisture from the air, which will clear the windshield faster. Just being in the car adds moisture, which can condense on the windshield. Even though cold air by itself is fairly dry, it gets 'wet' inside pretty quick just from you being there. There are not too many times that system would not be the easiest or fastest method to have a clear windshield. Make sure you're not set for recirculating and are drawing fresh air and you're pretty well set.

So the "just don't get it" people are wondering why someone would choose to make the system less efficient just for the sake of being able to. I *can*! put a momentary switch that bypasses the brake lights so they only turn on when I want them to, but it's not going to make things better just because I'm doing it manualy.

I'm all for doing things myself, and I'm fully aware that some folks would consider what I do silly. But if it makes me happy, who cares?

 

The efficiency part of it is the crux of the issue. When only a small amount of moving air at ambient humidity is needed to keep fog off the the windshield it is less efficient for the vehicle to run the air conditioner than only the electric fan.

 

Yes, I think the other part not getting understood is that you can still use defrost+ A/C, you just press the A/C button. Its the difference in using the A/C for defrosting when needed compared to always running it, needed or not.

 

I was going to add that they make the system user friendly by having the ac switch on. However, when user friendly makes things more difficult than necessary for what you would like to do with your device, it stops being user friendly. iPhone vs Android is an analogy that comes to mind.

 

Those of us with newer trucks that want to do this have to do the "control knob mod". I didn't invent this-it's been posted before.

WARNING: The A/C comes on with the defrost setting for a reason: the removal of moisture in the cabin air to quickly clear window fog. In like, now you can see where you're going, and avoid making contact with some other object. Proceed at your own risk.

As you can see the wiring is quite a bit different (2003 extra cab).


So you take off the control knob and file off the stop on the underside (or inside) of the knob. It's the tab that is opposite the indicator light. Sorry, I don't have a picture of that. I also filed off the stops on the face plate. (The two tabs that look like ear muffs)


Then you can turn the knob to the sixth position, which is defroster without A/C.


The compressor will not run in this position, but you will have full defroster function.

 

I guess a full disclosure statement for when I think this will benefit me would be when all I have to do is crack a window and boom, problem solved without any vent air. Sometimes I just don't want the windows open even a little or its raining hard enough I'd rather keep them closed.

 

Sometimes you need defrost with A/C. There are humidity/temperature ranges where you just can't clear window fog with humid air. But I've been using this setting every other time. I took the control knob off so I could turn to the extra setting. Now I don't have to.

 

Who would have thought something as mundane as adding the option to not turn on the A/C automatically would bring such controversy?

 

THIS^^^^^^
I did this mod too about 6 years ago. Don't know why other than to have the option. I found that the windows, on a rainy day, will not defrost-especially the sides and rear unless the A/C linked defrost is on, so I never used the mod again. A/C air is dry and does the job of eliminating damp air quickly. And when you increase temp in A/C link defrost, it'll come out warm so I guess those who are complaining about it must live in much colder climate than I do. Understandable.

 

As some have already noted defrost is a bit of a misnomer. I remember my old neighbor called it a defogger which may be a more accurate, allbeit rarely used, term. But we can discuss of the semantics of defrost some other time. I know what you meant and that is the important part...

You are very right, having the A/C on will remove moisture aiding the removal of fog/condensation on the inside of a vehicle. After you did this mod were you unable to turn on the A/C manually?

 

This mod enables you to turn the knob an extra notch to the right where it disables AC. All other settings for AC and heat etc remain exactly the same.

 

That makes more sense now...

 

Now we just need a mod write up for trucks whose AC doesn't automatically come on with the defrost setting. The mod would have the AC compressor always come on during defrost/defog for the people who insist this is proper.

 

I do not notice my AC compressor come on when I run my defrost. I have to physically turn the button on to get it to cycle. I've known more vehicles to have that option with the defrost as well. It's automatically wired to turn the compressor on when you defrost. The engineers have some reason behind it. Assuming it does have to do with condensation as others have stated.

Why would my 98 not have the compressor turn on when the defrost runs? Shoot - It could be I guess. I have the 3.4 and I actually feel very minimal power loss with the AC on.

 

When my A/C compressor turns on I can hear it and my rpms jump about 2-300. I don't know how noticeable it is with the engine you have, but my A/C light was always on when the defrost was on even if the button wasn't pushed in the light would be on.