Ok, so my 04 Ram has nice heat out of the vents....but when i switch to Defrost , the air up there is luke warm at best . Its putting out a good amount of air...just not hot

any ideas ?

In the defrost mode the ac compressor is running, but it doesn't in floor mode. So you may have a blend air door problem.

i read that the blend doors strip in these trucks....

replacing my broken ac/heat control first

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

I had a similar issue on an 04 I had a couple years back. I read all about the air doors and didn't want to really mess with that process. I ended up removing the blower motor from under the dash and reached up inside with my hands and found the air doors broken and just flapping around in there. I pulled them both out through the opening where the blower motor was removed and then put the blower motor back in and I had heat in all vents including the defroster which I did not have before. weird but it worked so not sure what the purpose for those doors are

I'm betting the AC leaves a lot to be desired.
The purpose of all those doors is to direct the air flow to all the available options (defrost, vents, heat, AC ducts, cool/hot and all the combinations of each) some people think they need.

My hot rods have a choice of defrost with heat, or off. I can regulate the amount of hot coolant flowing through the heater core, and I can control how fast the blower motor runs, or I can shut the whole thing off and open the outside vents. Gene