Ok, so today i flushed the heater core , it didnt seem clogged.

Ive replaced the ac/ heat control panel

I can switch the air between all the vents...but whats weird is the heat level is random.......sometimes i have half as.s heat on both sides of truck.....sometimes NO heat....sometimes only on passenger vents . Its seems random ?

Still no heat on defrost. Plenty of air flow thru all vents when switched .

so what controls heat to cold ?? one of the blend doors ? why would there be NO heat at defrost vents but sometimes at the others ?



UPDATE EDIT----

--- so i tried the method where you turn off the blower and switch between vents....wait 10 seconds and then fire up blower.....it worked !! great heat everywhere including defrost.

so....why ???? its got to be a blend door ? the one i heard moving was the one behind center panel... Mode 2 door ??

https://www.youtube.com/watch?v=LRJyQFuzvYM