I have a 97 f150 with the 4.6L V8 Auto trans.

I have been having issues with the heater and ac having a mind of its own and wanting to be cold when i have it on hot and hot when cold. This is not always the case and it will occasionally blow cold when i have it on cold and hot when hot.
this led me to believe that the control panel was messed up and id simply swap them out. No luck. so my question is where do i start looking. its starting to get cold up here and i have a feeling im going to need this heater soon.

A big thanks in advance.

 

Check for a broken temperature blend door flopping around.

 

I looked around and can't find anything. I did notice that its only working on panel and it did momentereally shut off when climbing. So could this be a plugged heater door as it seems now to only stay on a.c. and no longer have heat.

 

Check the vacuum lines behind the battery.

 

That would cause airflow to default to the defrosters, it would have nothing to with temperature control which is completely electro-mechanical.

 

You got me thinking and I decided to test the blend door actuator and it turned out that this was indeed a faulty part. I can now drive around happily with heat. however now that that issue is resolved ill throw another out there on the same vehicle any ideas as to why my heat or ac fan only works on the Hi setting and not any of the lower settings? Just a thought? Thanks again

 

That's the resistor pack.

https://www.tascaparts.com/oem-parts...r-4l3z19a706aa

 

yea I pulled it and it looked in good shape but I'm gonna replace it here soon to make sure thanks again. Will let you know