have heat on without it fogging up

2nd gen 15 taco (stock sr5 if that matters with a/c or heating options) I understand the science behind the fogging up but not 100% sure as to what to do to get it to stop fogging up. I turn on the car and run defrost and lower vent heat option then turn it to both lower and upper vents option (no defrost). I heard if i press the a/c button while running it this does something? I don't see how it does. Is there anyway to fix this dilema?

 

If you live in the place with humid air / you will have to use A/C to help de-fog. When you are in defrost than A/C is on. if you want the same when you set to lower+upper vents you will have to press a/c button even with heat on.

 

Not sure where you're from, but we deal with some shitty humidity year round. A/C button with heat helps dry out the air. Also crack the windows a smidge for quick de-fog then close them back up.

 

Blue is correct. When on defrost the AC automatically turns on to dry the air out before it blows into the cab.

I have a feeling that you're talking about getting fogging when you turn on the blower. That's because there's humid air trapped in the system from when you shut it down. If you're running the heat before shut down, then you're trapping warm moist air in there - which blows out and condenses on your windows the next time you use the truck.

It's spring time and there's humidity in the air. Switch to defrost for a minute before shutting down or just let your truck warm up a bit more before driving to let the fogging evaporate.

Let us know how it goes.

 

When you're in either defrost position and fan is on, the a/c compressor is activated. BUT, the a/c light does not come on.

 

Is your recirculate on? If it is...turn it off.

 

I never thought about having the heat on w/ the A/C button on/lit up. I just assumed that did nothing and just blew out hot air. Interesting...

 

It acts as dehumidifier. A C unit is before heater core when air is blowing, so when humid air hits AC cooler, moisture gets removed, and water drained out, next same air goes through heater core to bring back temperature.
All Dehumidifiers do that.

 

Like everyone else said, hit the A/C button and turn of recirc. The compressor drys out the air which will defog the windows. You can also run to Lowes or somewhere and get a container of DampRid and stick it in your truck somewhere.

 

that is great idea, also I would wonder if you have some kind of water leak in the cabin if you have a lot of moisture.

 

A 15 is still pretty new for this problem but make sure the ac drain line into the engine bay isn't clogged. That can cause moisture to build up in the system and fog up worse

 

Not necessary to touch the a/c button. When either defrost position is selected (ie defrost only or defrost/floor) the a/c is activated, but the button is not lit. When windows are defrosted/defogged, move the air control to any other position and the a/c is powered off.