[pulsar1230]

hi guys sorry if this has been covered before but i have not found the ans yet i have a e90 320d auto 2010 manual non heated seats just fitted leather heated /part electric ,got the electric movement bit done ok,but am not sure about one wire its the blue/violet on pin one of the under seat plug from what i have read its a pwm signal so where does it go, i have fitted the hvac unit with the heated buttons on it and ran perm 12v and ignition 12v from the fuse box to hvac,then ran ignition 12v,pwm wire,and 12 gauge [thick]ignition wire down to the plug under seats [also picked up a local earth at the seat mount],do i just connect these wires at the hvac onto the 14 pin spare plug and if so what are the pin numbers for each one as i didnt get a plug from the donor car which was a 2007,is there an extra box i need to buy which sends out the pwm [pulse wave modulation] or does that come out of the new hvac unit when you press the heated seat button any help would be greatly appreciated.