If I am not mistaken our temp settings work off vacuum. You might have a vac leak. Does your vent setting change on its own? Sounds like that sort of issue just a different fault.

When you checked the fan how hot was it? That is a thermal clutch and if its cold it will not allow the fan to turn enough to pull. Anything will stop it.

 

Since when?

 

My 01 has one, that's all I know.


ETA, Now that I think about it the shroud may be part the the aux trans cooler (which is between the rad and condenser) package.

 

When I checked the fan, it was warm enough that I think it should have been moving faster - I kept burning myself on the radiator coolant lines while replacing the clutch. Also, once it was replaced, the fan ran much faster than it did just before being replaced.

But you could be right about the vacuum - I had taken it to a mechanic, who fixed a few vacuum leaks, but I guess he could have missed one. I say this because I've noticed that when I accelerate hard, the vent sometimes switches to blow through the defrost, rather than the panel vents. I thought it was strange, but because I've never owned a truck before, I didn't know if this was normal.

 

I'll check for this, too...

 

Do a search on "wild vents", what you are seeing is 'normal' for our trucks. That does not imply that is how it is 'supposed' to work.