Golf mk4 internal fans not blowing! HELP!
 

I have a 1999 golf mk4 tdi and my fans on the inside of my car has stopped blowing and it does not work on all 4 speeds. I have checked the fuses on the battery and the fuse in the fusebox on the side of the dashboard and they are all ok. I have taken out the blower motor and resistor and replaced them both at the scrapyard just to see if they were at fault but still no luck and we used two blower motors and two resistors so its definately not them. Is there anything else i can check as I now have no idea what the problem is as the blower motor, resistor and fuses are okay. I have a multimeter ready but not 100% on how to use them/what I would be looking for. THANKS FOR ANY HELP!! :D:D