Lately on these cold mornings, I've been getting a lot of frost but it is on the inside not the outside! I'm guessing that there is a lot of moisture inside the cab. I had some moisture on the passenger side floor on the carpet but never got around to getting it fixed. What do you guys think is the problem? This is starting to really bug me.

 

The moisture is the cause.

It happens to my truck in the winter when I get in it with snow on my boots and the floor mats get wet when it melts and the next morning theres ice on the inside.

 

Try leaving a window or two down a crack, maybe 1/2" or so, unless of course, blowing snow, etc would be a problem....

 

If you have a power rear window, check around it for moisture, or just run thru an automatic wash and see if it leaks, i had that goin on. Wouldve never known if i hadnt got lazy and hit up the automatic one day

 

Be sure to run the fan on high the last 1/2 hour of driving before parking it for the night. If the moisture inside the cab is not a great volume, the fan 7 heat might dry it out.

You also might coat the inside of your windshield with that water shed chemical (sorry, cannot remember the name of it) that is made to use on the outside of the windshield. A light coating of liquid soap will do the same.

 

If all else fails, check the area around the heater core. If it is leaking, that may be the culprit.
I had a Buick that did the frost up thing. Wet mats was not it.
Change the vent setting on the heater control before you shut the truck off, from defrost to heat.
That helped. Leaving the vents on defrost caused any moisture in the heating system to condensate (and then freeze) on the windshield. Oh, and turn the temp control down before you shut it off.
Cheap and easy to try.

 

rain x