Does defrost in our trucks switch to recirc on straight defrost while floor/defrost is outside air? I'm having terrible problems with the windows frosting up badly on the inside and not thawing now that the temps are negative numbers. I have to scrape them with credit cards going down the roads and opening the windows to check for cars when switching lanes or turning.

Very annoying.

The reason I ask the above is that split defrost appears to work better than straight defrost.

Thanks!

 

Any chance you smell antifreeze or see a hint of steam coming out the defrost vents? I bet your heater core is all done.

 

make sure your a/c is working when it's on defrost and dont use recirc if your heater core is leaking it will smell like your old tackle box. recirc keeps the moisture in the cab so dont use it the ac removes the moisture when it's on defrost the a/c should be turning

 

I don't think the a/c turns on when it's -10*F (like right now, also snowing, and 45mph winds). Is it possible that there's snow in the HVAC air intake? Where is this located?

No coolant smell either and no steam from the vents.

 

yes the ac wil come on whenever the defrost mode is on no matter how cold it is outside . at that point it's not trying to cool you down but remove moister and all cars and trucks do it from the 80's to now. the air intake is under the wiper cowl

 

That's right! The AC does cycle to keep the moisture down no matter how cold it is outside when you use the defroster.

 

I am diagnosing the same problem. If I set the control to blow out on the face or defrost vents, it hardly does. Most of it comes out the floor.

I've changed out the vacuum check valves in hope of a fix, but not...

I am thinking it is either the blending door acuator motor, or heat-defrost door acuator motor, or panel- defrost door actuator, which ever one it is will be a major fix. Remove instrument panel and then remove the HVAC housing assembly, and so on.... yuk.... transformates to about a full days worth of work.

I am still reasearhing

 

I actually have no problems getting the air to go where it's supposed to. The heater takes a looong time to start putting out heat, though. I had the core flushed and they got nearly nothing out of it. It seems more like a humidity issue anyway.

This has only happened yesterday and today so perhaps it is just snow in the intake adding humidity...

Ugh. Driving today in the blizzard was bad enough but having to scrape the windows while driving down the road really made it horrible.

 

Is there actually heat blowing from the upper defrost vents when it is on defrost only? Maybe the actual mechanism that switches from one cycle to the other has come disconnected and it is not allowing it to switch it to the defrost only mode. I have read quite a bit on this before but have not paid enough attention to be able to tell you where to look and how to fix it. But one thing I can remember is that something gets disconnected that actually switches it from one mode to the other. Good luck.

 

I think there is a TSB on this for the older 2nd gens, and it was fixed for later model 2nd gens. something about blend door actuator.