I have read on hear in the past that the B5 s4 heated seates have problims and mine quite
My question is what goes out? I have a junk b5 a4 that the heated seates work just fine what do i need to do to swap brtween the two car to make the s4 seats get hot

 

Mine too! Just get a new seat.

 

Check the heating element in the seat, much cheaper than a new seat.

 

were is the heating element in the seat

 

yes. it's most likely the element....(thin ...aprx 10" x 10" paper like sheet that is located in the seat where the heat comes/used to come from,lol.... i would take the seat out of the car and then dissasemble the seat... or basically take off the covers.... i've found seat heater elements on ebay for pretty reasonable prices.... i had to change out the element on my gf's 99 vw jetta.... not too bad..